Phil - tried that, still same shceisse happening.
ST johnson - i tried it both ways. the vent is clear. so it must be something else
Hercmech - yours should have a vent. must be a factory mistake. i suggest you do drill a hole in it anyway coz it's supposed to prevent a vacuum so the lid doesn't cave and and so any remaining content doesn't shoot up when the lid is removed
Unreality - it's confusing. given what happened the first time round, you'd think it's a blockage somewhere (and it may well be). but to put it into perspective, i experimented by putting some water into the cup, put my mouth upto the cup and blew and the water started shooting out of the tip. it needed a fair bit of pressure but it defies the notion that it is a blockage.
Pawel - it didn't seem to matter wether the trigger was retracted or not. the content still 'boiled'. there was however a difference in frequency between retraction and pulling back.
Milairjunkie - you may have hit the nail on the head. ROO1 has always been a bit difficult to thread on, then all of a sudden it became a lot more difficult with more resistance and feels uneven when screwing it on. can't quite see the thread in the front of the body that R001 goes onto but R001's thread appear to be ok.
Hawkeye - when it first happened I had it upto around 15 PSI. during experiments afterwards, anywhere between 10 and 35.
thanks for all the input guys, appreciate it!
will have to take it to craig at the LHS and see if he can find the flaw.
At the end of the day one's work may be completed but one's education never!