2012 f150 intermittent no crank no start, IM STUMPED!

Hey everyone,

I drive a 2012 f150 for work and the thing is about to hit the scrapyard I swear.

Started in the summer, I'd go to hop in the truck and nothing, battery's fine, fuel pump hums but no crank. Took it to a shop, the replaced the starter, relocated fuse 27 and called it a day.

Just this last week it started again. Drove 4 hours to a job well away from home and yep. No start. I even tried jumping the contacts for the relay right at the fuse box and nothing. It sounds like the solenoid is moving and the starter is hitting the flywheel, but it's like it just won't try to spin the flywheel

When I called the local mechanic shop to have them take a look the tech told me he put a heat gun straight to the solenoid and it fired up. I do live in Canada and it was -35°C that day, but that wouldn't explain why it was acting up in the summer time!

So far I've: -Replaced the battery for brand new -Verified alternator is charging -Changed starter relay in slot 2 under the hood -verified fuses 28 and 13 -Replaced starter, (second shop recommends replacing the starter but I don't think replacing the starter annually is a solution...)