I've only seen the "bloom" once thus far. It was after about 3-4 hours of operation... it was working fine, i walked away, came back 10 minutes later and the center score section was about double the size and blurryish...
I immediately turned the machine off. I waited about 5 minutes and fired it back up. It worked fine for another 45 minutes to an hour or so when i turned it off. I've since run it about another 4-5 hours ... though only in 1-2 hour intervals... and it's not happened since?!
Other issues I notice but may be PCB related rather than monitor:
During the HS entry screen, everything gets all wavy side-to-side over on the "END" side... the vectors seem to have a "blink" to them.... not as silky-smooth as, for example, Asteroids or Asteroids Deluxe... more on par with Star Castle.. and there is a slight. Overall it looks pretty good frankly for not having been capped recently. I figured for a few bucks I might as well re-cap it and go from there.