Poor CPU utilization with M1 Max (batch edits)

[LOMOLCW]

I have the M1 Max laptop with 64gb ram. It has been great when I first got it. After some more recent Lr update, i found my synced adjustments are very slow. The screenshot is when I try to sync 20 raw files white balance. normally it is much fashter. I tried a few functions, and my utilization never passes 150% - with system reserved resources this barely use 1 full core power - not to mention that most of the resource used are efficiency core and not performance core.

this happens with dropper white/grey balance for sure, possibly other functions too.

anyone else in similar situation?

[LOMOLCW]

more context: I have NAS backing up this folder, but the files are stored locally in the MBP's internall SSD. I/O speed shouldn't be a constraint.