Hotend preheat error
Got my MMU3 a few weeks ago and added it to my MK 3.9. I was able to print many things without issue and wanted to try adjusting some volume purging when going from black->yellow. So I edited the purging volumes in slicer 2.7.4 to purge a little more when going between these colors. 
But it doesn't work. My Printer goes over to the wipe tower and looks to change filament, but in the process it reboots itself. It comes back with a big red error screen and a lot of beeping saying "Hotend preheat error #21202"
Going to this page it refers me to: https://help.prusa3d.com/article/hotend-preheat-error-13202-mk4-21202-mk3-9_401060
This error is shown when the printer is unable to heat up the nozzle more than 2 ºC for 20 seconds. The printer starts a safety feature, which instantly kills the heating process and displays the message on the screen. The printer then waits for the user to inspect all parts and if needed fix the issue.
There is nothing wrong with my printer. My printer heats up just fine and really fast. This problem goes away when I change back to default purge volumes and instead use global ones (editing the Filament Purge Multiplier in the Printer Settings).
Anyone else experiencing this? is this a Slicer issue?
RE: Hotend preheat error
🙁
Today I was 6 hours into a 9 hour print and it failed again. This time I didn't touch anything in slicer other than to increase the purge volume in the print settings for all filaments.
I put a multimeter on the heater: 16.7 Ω, and on the thermistor at 25 degrees: 100 kΩ
RE: Hotend preheat error
Same problem on my MK4 printer and MMU3. New model with deafult settings can't print -> stuck after 1st filament change -> change works fine, but after that it only travels short distance and restart with Prusa logo -> followed by beeping with mentioned error.. Example of sheep works without any issue.