Hetho, the 4 seasons is a great vent/hatch, if it isn't damaged then I would suggest it needs re-sealing - Butyl caravan repair tape is the best way to effect that.
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Possum; AKA:- Ali El-Aziz Mohamed Gundawiathan
Sent from my imperial66 typewriter using carrier pigeon, message sticks and smoke signals.
Likely find the fly screens haven't been replaced correctly. The fly screen needs to be well pushed onto the aluminium. Not easy to get the sides on correctly. Easiest way is from the outside. Need to have somebody watching from the inside to ensure you are lined up and then pushed on correctly. Can be done from inside with a little difficulty. RV makes that do the right thing have aluminium angle in front of the opening flap so when opening the flap clears the aluminium.