Here is something I observed and find a bit odd:
To replicate:
Have a substantial amount of releases loaded in the right panel. (some 20 is enough)
Select them all.
Click ‘save’.
Saving will be very slow.
Deselect all by clicking something in the left panel; saving speeds up enormously.
While saving is still in progress, quickly select all releases in the right panel again.
Saving slows down a lot again.
I think this should not be hard to replicate.
If it is, I could try to create a gif?