I have bought 20 Samsung s6 and after every 4 of them got stuck on Samsung logo, I keep them on charging for 2 days. Nothing work for me.
Since 5 of the Samsung tablets you received are working differently than the other 15 tablets, it's clear that either:
- Samsung has sold you a bunch of defective tablets.
- You received at least some counterfeit tablets.
In the comments, you mentioned that you believe you purchased them from a reliable source. If they are genuine, your experience indicates Samsung has a quality control issue... perhaps a serious one.
Return the tablets for replacements or insist on a full refund.
Note that I've purchased multiple Samsung Android products with serious problems, and trying to get support from Samsung was time consuming and a huge hassle. I now try to avoid Android devices made by Samsung.