Posts by @Esox about small "bumps" (from dropping the cap/head) on the underside of the top cap corners and base plates that are not straight prompted me to pull out one of my Old Types (at random) and check out the situation.
The base plate is straight against a ruler but, sure enough, there was one small bump under one corner of the cap which has, undoubtedly, caused some blade chatter and resulting harshness.
A small file, some judicious 'bump removal' followed by some Flitz and buffing with a soft cloth and things turned out pretty good.
I think I know what I will be shaving with tomorrow.
The base plate is straight against a ruler but, sure enough, there was one small bump under one corner of the cap which has, undoubtedly, caused some blade chatter and resulting harshness.
A small file, some judicious 'bump removal' followed by some Flitz and buffing with a soft cloth and things turned out pretty good.
I think I know what I will be shaving with tomorrow.