"N_Cook" wrote in message
news
I suspect they deliberately used non-matching threads,ie cross-threaded,
despite disassembly ideograph of a screw on the pcb overlay and red
nail-varnish anti-shake lock.
Even 2 minutes of soldering iron tip on the head will not free the locking
.
And of course buried deep in the case surrounded by all sorts, that block
access, to grind flat blade slots in the screw heads or pairs of flats for
mole-grips etc.

Might be worth reading the; "Best Philips screwdriver" thread.

Could be the crosspoint in the screw head is too shallow for the pointy end
of your screwdriver and the cross blades are only part engaging.

Screws can be tight, and a poor fit screwdriver will ruin the head.

Unless there's an overhead obstruction, you should be able to seat a drill
bit in the crosspoint recess and drill the head off. Removing the threaded
bit with only the thickness of the PCB to get hold of might be fun.

If you haven't chewed the heads up too much, drilling down with a pilot
drill smaller than the thread core diameter might allow you to turn it with
a regular Philips screwdriver. Or you could graze the pointy end of the
screwdriver a little with a grinder.