The caption blurring is on all channels and it will vary from clear and legible to very blurred and illegible. At the same time the main picture remains clear and sharp. If I watch the same channels via a recorder the same problem is apparent. This indicates to me the problem is signal related.
Not quite sure what you mean, "Used to be a "convergence" problem in the old CRT days" my TV is CRT rather than 'flat screen' and is capable of receiving both analogue and digital signals. Prior to the analogue shut down, all captions on both were clear - this problem has only become apparent since only a digital signal is available.
I'm not sure I understand what you are saying. To tune the set there is a menu item that searches out all channels available and locks them into 'memory'. To my knowledge there is no manual 'fine tuning' for individual channels - the manual tuning is only for all channels as far as I can make out. If I select either 301 (with picture) or 302 (shows text about 2012 Olympics only) they are both blurred for the text as any other channel. Does this mean there is a fault in the TV? If it's of help the TV is a Sony Trinitron KD-28DL11U.