I have a 24 VAC transformer powering two Jandy pool valve actuators.
I have both hooked up to a single pole, double throw switch. Flip the
switch one way the the actuators move until limit switches inside turn
it off. Flip the switch the other way, and it puts power to a
different lead to the actuators and they move the opposite direction
until the other limit switch shuts them off.

One of the valves goes 90 degrees and the other 45. Problem is, when
the one gets to 45, it does not switch off but instead oscilates back
and forth switching directions until the 90 degree one stops. Works
OK, but I'm afraid I'm going to cause damage. I looked at the manual
and it specifically says not to double lug the switch leg wires as I
have done. That I should get a double pole switch. However, I can't
figure out why it should make a difference. My switch is far away, so
hooking it up the recommended way would require a run of two
additional wires which I'd prefer to avoid.

Here is the internal schematic - in section 7.1 and how it should
really be wired up. Any alternatives?

http://www.jandy-downloads.com/pdfs/JVAmanual.pdf