Philips AG1016 turntable will not stop, keeps repeating

After the creation and mounting of a new belt the device works fine with the exception that it will not stop otherwise than by pulling the plug. At the end of the track the arm is lifted and turns beyond the store position and next starts the disk again as if the button were on AUT and not on STOP. It very rarely occurs though that it stops. Any hint pointing to the spring or other lever to check is welcome.