The issue was discussed privately. I determined that Edit Post Date by Waindigo was causing a template modification compilation error for several different add-ons, and that Poll Permissions by AndyB is incompatible with my add-on. With both of those disabled, Slide Out Poll works correctly.
I do not know what the problem is with Waindigo's add-on, but I don't have any intentions of making a compatibility fix for AndyB's add-on. However, I think the application order for the template modifications can be changed so that my add-on goes first and AndyB's goes second and then they don't conflict. I'm not sure.