I have been experiencing a weird issue with my MK3S / MMU2S running PrusaLink on a Pi Zero W.

At first glance, everything works fine. However, a random issue happens when I send the g-code file to the printer via PrusaLink / Prusa Connect: Right after the mesh bed leveling is complete, the extruder head rapidly moves back the origin (lower left corner) and lowers itself to start the purge line.

Immediately after the G1 Z0.4 F1000 command from the default start g-code in Prusa Slicer MK3S profile, the print head quickly lifts back up and move all the way to right for a filament change, even before the MMU2S loads the assigned filament in. During the slicing process, I pre-select the filament in the slicer so I do not need to select it from the LCD screen (Could this be the root cause?).

Originally, I thought the issue could've been triggered by either the FINDA or filament sensors being not well calibrated, although very unlikely. But, to rule this out, I copied the same gcode file into the memory card and ran the print job again, without touching anything on the printer. It turns out that, when running the file from the SD card, the issue never happens.

This morning, the issue happened when I was testing the MBL from Prusa Connect to check the bed leveling. No file was being to the printer other than G80/G81 commands. So it is definitely not a sensor problem.

This leads me to think that the issue is related to PrusaLink directly, as it is acting as the host to control the printer by sending the gcode commands.

Any ideas?

TIA.