Rename the add-on from `flamenco3-addon.zip` to `flamenco-addon.zip`.
It still contains the same files as before, and in Blender the name of
the add-on has not changed.
Move the old worker out of the way. This should keep the old executable
as-is on disk, hopefully keeping currently-running processes happy.
I've noticed some workers crashing as soon as the executable got
replaced, which made me suspect that it's not 100% loaded to memory
before starting the execution. Let's see if this works better.
