This is what I have found - if you have noticed the switch off & reboot times have increased somewhat this must be dismounting & re mounting the SD card. Not a problem as it has fixed all isues (for me anyway)

Hello Kuririkura,

I think it won't take the lenovo update maybe because the device is rooted? (because you have twrp?) The solution was to unroot it, then it takes the updates again. Then root again.
I'm not sure how this proces goes, because I haven't rooted it yet.

Hope it works!

With this issue seemingly solved on the Tab 4 8 Plus and me being quite happy with the results - I purchased a Tab 4 10 Plus for the added screen real estate. Guess what - it has just destroyed another 128GB SanDisk Ultra card. Lenovo that's another £50 worth is SD card ruined. Your hardware is troubled & people need to be aware of this. Lenovo never again for me - I have had enough of your poor hardware - EVERY tablet you have produced has had some sort of problem yet you generally care nothing about your customers. 

Moderator comment: Post edited to conform with the Community Rules. Keep it clean and no campaigning.

I have now lost two 128GB cards to Lenovo tablets that is over £100 with of card to me. My Tab 4 8 Plus destroyed 1 plus a 64GB and now my Tab 4 10 Plus has just destroyed another SanDisk Ultra 128GB. Lenovo need to be brought to task over these issues but I fear they will hide behind corporate closed doors as per usual.

Moderator comment: Post edited to conform with the Community Rules. No campaigning.

I too have the same problem with Tab 4 10.  Worked ok for a couple of months but now corrupts cards or shows the dreaded 20% error issue. This occurred with 2 new 32Gb Lexar cards and a new 64Gb Samsung card.  I am not prepared to waste any more money on cards.  Time to move on to a different tablet I guess. That is once I have enough money!!!!

I've just recieved my Tab 4 8 Plus LTE and am experiencing similar issues with the SD cards. I note that some have mentioned that they have used Sandisk cards , and they seem to have the majority of issues.

As a retired Systems Engineer , I also know that there are many counterfeit "Sandisk" SD's out there , and they simply do not perform.My Kingston ones have not missed a beat , either formatted in the tab or Win 10 , but my genuine Sandisk ones all had issues. All cards used were rated "10" , a somewhat useless rating IMHO. Same said for a couple of "cheapie" cards.

There are a number of utilities out there that you can use to examine the origin of the SD card you have , and I'd suggest the people test them before ever using a card for important storage purposes.And I'd emphasise the need to rigorously have Backup procedures in place, the cards are cheap compared to the Data you are putting on them.

All that said though , the entire mechansism , hardware & software seems to be problematical and there is known history here. I also have an older Lenovo tab , the Medion Lifetab S7852 , and frankly , it's never missed a beat , still going strong today (just Zero support from Lenovo) It simply does not care what type of card you throw at it.

My tab has the most current firmware TB8704X_S000037_180203_ROW , but sometimes I'm reluctant to follow the path of always taking updates , as I've experienced the failure of many in the past , you are simply better to stick to updates that exhibit the fewest of issues before getting the latest. I.E. let others leap in first !

So , the sorry saga of the SD card issue has not disappeared , even with the latest update , so Lenovo , if they care anything about reputation , need to address this issue with quite some speed (I live with an irrational sense of hope ! )

Otherwise , I like the tab , all the other functions work well for me , I would like to buy a spare SIM tray , but these seem to be from Unobtainium , listed on the parts site , but not purchaseable ! Talk to me Lenovo !

Have now completed many tests of SD cards in my TB8704X Plus 64GB LTE and concluded the following: It does not like cards that are too slow , too fast , or have latency issues.

The only reliable cards I've used that show any consistency are Samsung & Kingston (32~256GB Class 10 Spd 80~100Mb/s).

All others had various issues so I did not bother to test them further.(Lexar, Sandisk etc incl. no brand)

Test rating was done using WIN10 64bit i7 machine , and a USB3 card reader , no other tasks running.

My only real beef with Lenovo is the difficulty of obtaining a replacement SIM/SD card Tray , and if it's available the outrageous price they want for one. I could have done these tests rapidly if I'd had 2 SIM trays to swap cards , but with just one , it's so fiddly !

32GB microSDHC Class 10 (TS32GUSDU1PE) card has been working reliably for me since early dec 2017. I have it formatted as internal storage. I have two Tab4's and both of them have this card.

I've had my Tab 4 Plus 8" fry three uSD cards so far. One 128GB SanDisk, one 128GB Samsung, and a 32GB Lexar. The Samsung was toasted beyond rescue after the January update, and the Lexar one corrupted, but rescuable after the Feb update.

Either way, I don't want to have to spend money on a Transcend card to get around this shoddy QA.

At least if it could be confirmed if this was a hardware or software issue it might give us some options other than straight returning them all.

Hi Enigma,

                   well , you've only got a couple of options , return the unit for a refund ,or keep it and try to work through this. I do one thing with all SD/MicroSD cards I use prior to actual usage , I slow Format them in my PC first , do a CHKDSK after and if all is ok , proceed to use them in whatever environment intended , but formatting in that intended device for its use.

                  The reasoning is simple , the slow format actually formats , where the usual "format" is a "quick" one that simply writes to the FAT table and finishes. The "quick" format creates a problem if the original formatting is not solid or somehow incompatible with your device.

                  I've used this techique for many years after experiencing failures in many media type over many years in the computer industry.Whilst the media supplier always will tell you their product is reliable , my experience is that is fanciful at best.

                 I'm an old school Engineer , I believe what I can see , hear and touch , the hype is usually that , hype !

                 Like they now all claim 1000bytes is a Kilobyte , not the 1024 it should be. So if they are prepared to rewrite definitions , guess what else they are probably rewriting. 

                Maybe try some "no brand" cheapie cards and see what they do , I did , some kinda worked , others simply failed outright , but at least you won't be out of pocket much and will have further proof of product failure. Always take screen shots of the process to back up your claims.

               I would echo the many others who have lambasted Lenovo for its poor support (and I used to work for IBM in the past , those guys would be turning in graves now from embarrassment !) and it's poor attitude to after sales service. Even buying parts listed on their own webpages is too difficult for them.

              I wish you all the best , hope you get it worked out !