Quoted from Squizz:Hmm I was told from Pat at Stern that it was the shaker moving the hammer back up and then a slow down again.
I don't know, Why would it raise again if the coil is holding the hammer down.
Installing 1.51 again now to see if it changes
If it's the shaker I would unplug it from it's board on the lower left of cab and see if the hammer behaves correctly.