Like some others, I found that some PL-13 switches could be problematic with PL-10E motors - in my case mounted under 1/2 inch plywood with a thin cork roadbed. I eventually concluded that too much play in the motor armature was conspiring with sticky switches to limit the throw at the switch. In one case, I replaced the motor, but otherwise I have been able to fix the problem by disassembling the switch, retensioning and (very!) lightly lubricating the slider with teflon grease, and filing out the slot in the PC board a bit to get a longer throw.
Those that have had this treatment have been working fine for several months now.
Good luck, Mike