Hey Andy,
even if it comes too late:
sometimes it helps when you work with heat and cold.
You could heat up your hex wrench, stick it into the hex screw head, heat the screw for a while, then let it cool. It may have loosened the screw in the thread and released the Loctite or Superglue or whatever it is a little.
Or you can use hot air gun to heat the plate and then cooling spray to cool your hex wrench, stick it into the screw in order to cool it.
Also an impact wrench does me good service sometimes but mostly on larger devices.
In every case it is important to have high-quality hex wrenches. I have cheap and pricy here, and I can tell the difference!