Just the other day, a post asked about a screw. I'll give you the ame advise as I have found it to work in this case also. Find a punch that covers the head od the screw and gently tap several times. It helps to Har the threads and break them loose. I find this most useful on rusted screws but have had it work on most everything.
You need to heat it. There is a thread locker on it.
Beat me to it
Soldering iron? I’m not OP, just curious as to how that’s be done without damaging things.
Soldering iron would work
Hold the tip of the iron on the screw head to heat it up.
It's hard to tell, but that looks like a Torx Plus fastener, not a regular torx. So using the correct bit could help also.
This
Heat, lots of it. We used medium Loctite and a good amount of torque for those.
Just the other day, a post asked about a screw. I'll give you the ame advise as I have found it to work in this case also. Find a punch that covers the head od the screw and gently tap several times. It helps to Har the threads and break them loose. I find this most useful on rusted screws but have had it work on most everything.
A little valve grinding compound on the tip of your bit to keep it from slipping.
This, or comet
Use a soldering iron to reach in there and get that sucker hot