I have a Sample (or early production EarthShaker) that I have restored with a new playfield cabinet decals etc... I was working great until the sinking building started having issues. It sometimes would not move or would move but with significant motor noise. It would always fully drop or fully exstend when it did work. I first changed the 3906 transitors did not fix it. Then I changed the motor that seemed to correct the problem however now I'm getting a switch error for opto2 which is the height switch and the building only raises half way. I changed the opto did not help. In testing the optos they only register in the switch test upon exit of the blocking portion of the opto interuptor. in other words when the interuptor first block the opto beam nothing when the interuptor exits the opto it the registers which causes the motor to stop and the building is only half way. This exists in both optos.