Could it be that the sliding covers often break, and get glued firmly back into place ?
Can’t judge of your region from this distance, but could all second-hand Xantiae
in your area have passed through the hands of the one same mechanic using the same ‘specialist’ trick ? 
I certainly had that situation when working for SONY in Sydney nearly 20 years ago.
I used to moonlight in several different competing places, and some models always fell into my lap, no matter who they had called.