Thx for your reply.
The device times out. There are no miscalculations reported, neither before not getting any results nor while it tries to recover. Looks like this:
[...]
Antminer (COM9) ERROR: Selftest error. Timed out at 25000 ms.
Antminer (COM9) ERROR: Selftest error. Timed out at 25000 ms.
Antminer (COM9) ERROR: Selftest error. Timed out at 25000 ms.
Antminer (COM9) ERROR: Too many errors, giving up
As I said when starting the device manually again it does work. I will try to setup some regularly scan intervals to get it back up.
This may be a heat or voltage stability issue but when I saw that, I find that if I back off the speed one step at a time, I can find a speed that it will run 100% reliably at.
I've got a U2 that won't run at anything over 1.8 but I've got U1s that run at 2 with no issues.
Also verify that the connection to that miner is solid. I had to use some short USB cables to be able to fit mine all into my older Anker hub and found two bad cables causing issues.
2 out of 20 cheapie Hong Kong eBay 6" USB extension cables isn't too bad but tracking down the issue can be annoying at best.