I've recently had a mustang bridge professionally installed on my Jazzmaster to get rid of all the buzzing and general ****tiness of the jazzmaster bridge...And even though the Mustang bridge gets rid of these problems it's still pissing me off...

For some reason the top E string slips out of place on the saddle CONSTANTLY...

I've looked into it on the internet and few people have this problem, most people just say to not play as hard, but it literally falls out of place no matter what strength I'm strumming.

Does anyone have a solution? Would thinner/thicker gauge strings fit in place better? Should I file it?
well, i use graphtech saddles on my jazzmaster, and 11-48 gauge strings, and that works for me, but the graphtech saddles probably won't make any difference for you since they are slotted just the same as a mustang saddle and the string will probably still pop out. unless you're already using 11-48 or heavier i don't really know what to suggest, other than installing a buzz-stop (something i may do to my jazzmaster just for peace of mind because lately i've found myself playing it a bit too carefully to avoid such problems, even though i've not had a single problem since i installed the new saddles.. and that was about 7 months ago)
I like analogue Solid State amps that make no effort to be "tube-like", and I'm proud of it...

...A little too proud, to be honest.