Streaming Stick(s) lock-up daily

"Sticks(s)" as I have four of them exhibiting this behavior and it started at the end of April - on all four.  Family is getting really grumpy about these devices. I've had Roku for years, and suddenly they are all failing.  At first, I suspected a faulty software update, but surely if more people we experiencing the problem, they would have fixed that by now.

All of them:
- are plugged into the wall, so let's eliminate TV USB power problems;
- are Streaming Stick 4K plugged directly into HDMI;
- run for a day or so, then "freeze" - that is, they fail to respond to the remote - the screen saver may be on or not and pressing Home or Back has no effect;
- can be restarted by pressing the reset button to restore control;
- lock up after non-use - never while being actively used;
- are connected to wi-fi - in fact, the most problematic Stick is 3 feet away from the access point, so distance does not seem to be a factor;
- have the most current update because they are always connected to the Internet;
- are connected to HD TV's, except one, which is 4K;
- have fresh batteries in the remotes and the remotes are verified connected by looking at the green light under the battery cover upon reboot;

One of them started locking up every couple hours, so I replaced it with (silly me) another Streaming Stick 4K that has the same problem.  In troubleshooting this particular Streaming Stick 4K, my wife was able to perform a master reset on it, and the problem continued.

I opened a case with Roku: Roku Customer Support reference #: 7760908 which was escalated to higher support and died.  Support claims to have not received the information from the devices, despite sending them photographs of the issue ID's (D3-255-976, K0-255-975, 3C-255-973).

I cut the cable and the fam transitioned easily, but they getting grumpy.  So...what are my options?  Replace the Roku's with ... what?  Obviously not Streaming Stick as I can take one new out of the box (I had a couple spares - Amazon had a Black Friday deal and I bought several of them) and it does the same thing starting the next day.  Considering Roku's lackluster escalated support, I'll cheerfully jump ship and do something different.