Since the old crystals work and the new ones don't obviously points to the new crystals and nothing else. There may be nothing "wrong" with them per se, just that they weren't cut to OEM specs for that particular scanner. That type of crystal hasn't been in production for years, the manufacturer had to dig out what was left of the old design records and cut a special order. That simply means generic (more or less) or in other words good enough for government work or "gee, I hope this thing works". They tested just fine and were shipped but that's not to say the test circuit exactly matched the oscillator in the scanner, they work but not in that particular circuit being it doesn't quite have the "oomph" to excite them.
The bottom line is this is fairly common when something is long out of production and engineering no longer has exact specs to go by. Crystals have come a long way only they've taken a completely different direction and old data has been archived and annotated to save storage space.
Now have you stopped wondering? (;->)