Random and annoying . .

So my wiper switch had been finicky ever since I got my Mustang. It finally went out last week.... I ordered a new one and installed it last night. It works a bit better, however, the wipers will stay on after I turn the switch off!! It doesn't happen every time, it usually only happens at higher rpm's/current. I will turn the switch off, and it may cycle 1-2 more times and then turn off or it may just stay on! So frustrating.

One thing I noticed is that the driver's side blade acts a little strange. If I turn them off, (and the blades actually stop) when the D. side blade reaches the bottom of the cycle it will actually bounce back up an inch or two, whereas the passenger side blade just stops at the bottom of the cycle as it's supposed to. My thought is that this acts as a sort of flywheel effect. Perhaps it is 'bouncing' up enough to make the blade cycle up/down again, and it just keeps 'bouncing' back into the range where it automatically cycles again?

Anyone ever heard of this happening? Any suggestions?