cyclone display gradually fades in

[robm]

My cyclone display is rather temperamental - sometimes it works fine, and other times it takes 7 - 10 minutes to work BUT, its only a few digits - mainly 1st and 3rd of the top two displays.  At first they don't work at all, then the 2nd comes in fairly quickly (after 2-3 mins), then later on the 1st and 3rd start of really dull, then after another couple of minutes they are as bright as the rest.  Any ideas what the problem may be?

[Retropin]

Sounds like you have a high resistance joint. I was tempted to say that the displays are out gassed ( gas burnt out), but this cant be the case as the neon gas is to the whole display, not single characters.
Are there any burn spots at the displays in question?
If not look for cracked joints at anode and cathode to the ones in question... it sounds very much like the "high" voltage is struggling to get through here

[robm]

Sounds like a good description of whats happening - had a good look over all the connections this morning, and everything looked pretty good, with good contact between the board, component legs and solder.  No burn marks that i can see on the displays.

Of course when i turned it on this morning everything worked fine - should i wait until it does it again and test voltages somewhere - if so where?