Does it appear like they are desperately trying to shove the core into the composer without success?
That's normal when you use 4 fast inserters, three is fine.
It's due to the change from previous versions where the composer locked all additional cores once the area above was full and the towers had a limit.
Now it buffers.
Stick to three fast and you're fine, it's max speed for composers
#Inserters bugs
thorny lotus
thorny lotus
I had the same experience while my power usage was just 10% of the production, though. But maybe the severity of the issue is increased in that case