Originally Posted by
clough42
There are a few things that can cause this.
1. Power issues: The Pi needs a solid power supply. The 5V regulator on the Arduino will not suffice. If you have an ABL servo, this will make things even worse. If you cut D1 (RAMPS) and power everything from the 5V rail of your supply, you should be okay. Running separate wires from the supply to RAMPS +5, RAMPS VCC and the Pi is best. Using a cell phone style supply for the Pi is probably also fine.
2. Timeouts. If you run an ABL sequence at the beginning of your job, OctoPrint can give up because it isn't getting anything back from the printer during the sequence. If the carriage is high and it takes a long time to get back down to zero, the same can happen. Increase the communication timeout in OctoPrint to fix this. I think mine is set to 150 seconds.
3. Floating endstops. If you have your max endstops enabled with the pullups disabled, the printer will still work most of the time, but they can false trigger with power rail noise. Make sure your max endstops are disabled in the firmware if you aren't using them.