Used to figure hairline cracks were no big deal and flexible caulk would hide them fine. Three years later mine came right back along the same lines, so now I'd get a plasterer out to check what's moving behind the wall first.

Man, old gear just had some magic that new stuff can't fake.

That "plastic fine tooth comb" trick is the real deal, my old shop kept one taped right to the station for this exact reason. Running the blade backward through the teeth scrapes out the packed hair and gunk without messing up the alignment, so you get a few more cuts before a real swap. Saved my butt on a busy Sunday more than once.