SOLVED: Leaving USB plugged in to windows caused reset problems (original MK3s) post upgrade to firmware 3.8.0-2684 (maybe only when Cura running)
Just finished my printer last week, decided to upgraded my firmware to 3.8.0-2684. Everything was great for a little bit. Then I was trying to get a really smooth print and wanted to coast. After a rabbit-hole exercise of what to do I decided to use Cura. I had left the USB from the printer connected to my laptop-- I was not using this, I was not printing from my laptop, it simply was left connected. I have been only printing from the SD-card and only connected my computer to upgrade the firmware.
From then on I had random restarts and sometimes trouble selecting a print on the sd-card-- I'd select it and it would immediately restart (as if I hit the "X" button). Sometimes it would start the print and then freeze 2 seconds in, sometimes 10seconds in. In any case it would freeze, but the LCD would work and I could "stop" the print and do other stuff.
I was starting to feel like I was going crazy as it was working so well previously. I wanted to blame the firmware. I wanted to blame the power supply. I wanted to blame the SD-card.
I only noticed the actually issue because I decided to downgrade the firmware and when I tried to connect with pronterface it couldn't get access the the COM port. So then I noticed that cura was holding the COM port. Then I had the "aha" to try it once more after unplugging the usb.
Solution: unplug the USB cable when not using it.
I relay this in the hopes it helps someone else.
RE: SOLVED: Leaving USB plugged in to windows caused reset problems (original MK3s) post upgrade to firmware 3.8.0-2684 (maybe only when Cura running)
Some programs (pronterface, esp.) do not respect busy status and continue to query temperatures via M1xx commands.
This can corrupt the buffer and they get interpreted as M1, which is "pause" and generally cause all kinds of havoc.
Don't use pronterface or other USB status programs when printing from SD.