Summer Heat And Door Locks

[TnLex13]

During the summer my drivers side front door lock won't lock or unlock except when I do it manually.

It will sometimes lock or unlock once, then its like the actuator is too weak to do it again and I can't figure out why.

The other doors will lock and unlock numerous times and then they seem to get weak and finally they will stop working.

And all this only happens in the heat of the summer.

Any ideas about how to fix or remedy this is appreciated.