Error compiling to teensy 3.6
I found a fix, it's not elegant or easy to use, but it works.

Steps to take

-Install a fresh version of teensyduino

-Make a copy of [arduino directory]/hardware/tools and save it anywhere as a backup (sometimes weird, buggy things happen)

-Make a copy of teensy.exe from the tools folder, and put it in the same directory as arduino.exe

-every time you run arduino.exe (don't double-click on a .ino file), first start teensy.exe and everything should work.

Sometimes, the tools directory gets deleted (It just seems a bit buggy), if that happens copy the backup and paste it where it should be ([arduino directory]/hardware/tools)

Also occasionally teensy.exe gets deleted, so make sure to have a backup of that as well.