I'm new here and just registered on the board to share my recent experience on the topic. I hope that my info might help you!
I bought last year a TS-653B Nas and I'm pretty satisfied and happy with it since. I'll try to keep the story short, so soon after I've bought it I sourced 2 x 8GB DDR3L RAM - Crucial.
I've replaced the stock ADATA RAM modules with these after I've ran memtest for a few hours or about 3-5 full passes with all tests selected (can't remember already the exact number of passes or the hours it took).
I'm running the NAS with the Crucial RAM since than without any issues until around Christmas 2019. I wanted to make some changes in the drive configurations/setup and to reinitialize the OS/QTS on SSD, also I had an issue that when I select to shutdown the NAS, it actually restarts gracefully instead, but 3 of 5 times it didn't power off and just restarts.
So I decided to upgrade the firmware prior reinitializing the QTS to see if this will resolve the shutdown/power off issue. Earlier (maybe in the end of the September or the beginning of November) I was upgraded the FW and QTS to 126.96.36.1994 build 20190918 and used this version stable without any issues that I've noticed, except the one shutdown one.
After the FW upgrade to the latest version 188.8.131.526 build 20191206, re-init of the QTS, all configurations from scratch re-attaching my RAID arrays and so on... I've started experiencing random reboots of the NAS and unclean filesytems every 2 to 3 days, sometimes even under 2 days uptime.
I've then googled the problem and found this topic and soon decided to downgrade the FW/QTS back to 184.108.40.2064 build 20190918, because I was in doubt that the RAM could be the problem, as my usage cases and conditions did not change during the months and after the recent changes. I wasn't installed or used anything new as app or major setting that could cause unusual RAM usage.
To the point - finally I've detached my data RAID arrays and other disks and downgraded the FW/QTS to 220.127.116.114 build 20190918 only with 1 x SSD as I always install the NAS and reverted the all the settings from previously taken backup of them before FW downgrade.
Almost everything went OK with restored settings and after post-configuring some minor things I've re-attached my other disks and RAIDs and so far I'm happy to report that 6 days so far - there are no random reboots!
For me QTS to 18.104.22.1684 build 20190918 hold OK for now downgraded back to it and was holding OK for about 2 months before I upgrade to the latest FW/QTS.
I'm not going to try newer version prior the last one for now as ever back and forth of FW change costs me about a day and I have a lot of TB data that I don't want to loose in try and error aspect...
I hope this helps if someone wants to be on QTS 4.4.1 and wants to spent some time to try it! Wish you luck and if there is more info that I could help you with, I'll be glad to share!