My upper right flipper started to stutter like this recently:
At first I thought it was a broken EOS switch but after closer inspection, I noticed that the stutter was not happenning while holding the flipper up and keeping the button activated. The EOS switch was well adjusted too.
In this case, the low voltage section of the coil was broken. There was no power after the EOS was triggered so the flipper would come back down then up as soon as the EOS closed since high voltage was still working, causing an infinite loop.
Took the old coil out, installed a new one and the problem was gone:
The bad guy: