A couple years back... I had a Wren 44 that would flame out at randome times. I couldn't figure out what was wrong... so just for giggles, I put a felt clunk on the main tank and removed the bubble tank. (to reduce the suction needed) After that... it never flamed out again. I eventualy made a small 2oz bubble tank, and it didn't give me any issues.
My thoughts on it were...
1) Too restrictive with a bigger bubble tank.\
2) There was a slight leak in one of the hoses, or the bubble tank lid.
Anyway... I would personally remove every fuel connection, and re-fit. If you have festo fittings on the suction side... they can leak. (They were meant for pressure)