I do the same. I have the same issue and wired it to INT2 as well. I never knew it was related to start/stop. I will try to turn start/stop off on my next long drive.I've only done this once when I forgot to disable start/stop, but it worked: I flipped the INT2 switch to off, gave it about a 5 count, then flipped it back on and the mirror turned on.
I think the long term solution is hardwiring it to the fuse box or battery, but I've run enough wire for now. I'll revisit it in a month.