After 14-15 years , things are probably getting a lil worn in there, even without turning the wrong direction with the key halfway in.
Is the cl still ok?
My last car a 98 tigra was key open cl no plip plip.
The boot lock went about 4 years ago and I just converted it to being unlocked..trusting soul..
Options without replacing.
Maybe try a small amount of vaseline on the key and try and wiggle it gently in the right direction,n maybe some vaseline on the mechanical bits you can reach.
Check that the latch/part tchat locks onto the body isnt clogged up with dirt and works ok with the door open.
(Key itself could also be worn a bit).
The linkages could be strained by now,grooves worn etc.The mating surfaces sometimes have plastic grommets on them and they could be gone
As a last resort unless you are going to strip the mechanism:Use wd40 ,with the little injector tube attachment to lube the internals.
The trouble with something like wd40 is it may dissolve any thicker waterproof lubricant.