It doesn’t run “forever” on my A1 mini. It does run for a long time though. As best I can tell, this is actually normal and expected behaviour and does seem to end up with valid flow dynamics calculation. I certainly would agree though that it’s weird and probably needs some form of addressing.
My guess is that the changes in pressure are more subtle and take a lot longer to ascertain with a 0.2mm nozzle. I also guess that once the blob gets so large, then surely it would begin to mess with the measurements. On the other hand, this may be intentional as a way to approximate the back pressure presented by the print bed or previous layers during prints. It would take longer for a 0.2mm to squirt enough filament out to create such a blob for back pressure measurements, if such is in fact the intention for the process.
In the meantime just don’t turn on Flow dynamics for the 0.2mm nozzle — or let it complete just once, as I did. Run manual calibration instead.
Oh and yeah … the first couple times I tried this, I turned the printer off, thinking something just HAD to be wrong. A perfectly reasonable response I feel. 