Vertical stabilizer wont come out (Asw-19)

Hi,
I was wondering if anyone experienced anything alike before and
might have any useful insights:
My vertical stabilizer on the Asw-19 has always been a problem when
being disassembled and has always required little more force to remove
than it was called for. Anyways, today I have assembled a glider and I
was unable to remove it again - we have spent close to 3 hours trying
to unhook it from a fin. Has anyone experienced anything similar
before? Any ideas? I’m afraid it wont let go without breaking the skin
on the fin and punching the locking pins out directly...

Thanks

GK