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 !