Ok, I misunderstood your problem, sorry. Downvote removed.

Just put them on different keys.
They are on the same button by default, but you can separate them. You should've checked the controls first, before opening a ticket...

Same things here.

I got my 750ti in september 2014, the shadow bug appeared. But after a few months, the bug was gone.
Until this autumn. Now it has returned with an nvidia driver update, and it is still there.
Only sollution to use an old driver, or turn off shadows completely.