Not sure if you've had any replies to your query. I have a 2023 320G with the 3 season doors. We love them and use them often. We've found the fit of the doors is very sensitive to several factors independent of the rubber seals and brush "seals" at top and bottom.
When we purchased our new 320G, it did not have the doors. We had them added as part of the package by the dealer. Their first attempt left a large gap at the bottom on one side. Not sure what they did wrong but we found it at our walk through and made them fix it -- which they did. Perhaps your initial installation wasn't to spec? Something to check if nothing else can explain the problem.
However, assuming the seals and brushes are in good shape, AND the original install was correct, I'd look for a bit of frame twist or deformation in the rear. As we've struggled with our Lippert self leveling system (that doesn't self level half the time without a fight) we've noticed even a slightly unlevel and twisted frame can be enough to affect the fit of the 3 season doors. I'm not talking about enough twist to damage the frame. It apparently just doesn't take much twist at the jacks to create fit problems for the 3 season door. Ours is pretty sensitive. Its also worth pointing out the doors themselves are finicky. They are NOT self centering as I'm sure you've discovered and can easily come off their upper tracks if opened too far. Check to make sure all door panels are properly seated in their roller tracks for solid alignment and that they stay centered (when closed) for best fit.
With these things considered we've been able to keep our doors fitting reasonably tight in the frame. That said, like you we can have small gaps; especially at the bottom at corners even under best of conditions. According to the dealer, and confirmed by other owners who I've talked to small, dime sized gaps at corners are not uncommon.
In spite of those nuances, my wife and I have found the doors to be very rugged and functional. With the summer heat, we really enjoy sitting in the garage space (configured for living area when our toys are not with us), sitting at a small table sipping coffee watching the water flow by from our air conditioned space -- completely bug free! Great way to start the morning for an old retired couple
I hope this is helpful.
v/r,
Larry
PS: If you haven't discovered I'l add to always remember to lower the glass panels in your doors to their lowest level before traveling. The spring clips that hold the windows in their up/closed position are known to fail under vibration with a resulting broken glass door when the glass suddenly falls to the floor. I reco you add this to your predeparture checklist.
Also, if like me you'd like a way to lock your 3 season doors I found a small but sturdy lock on Amazon that works nicely. Its not weatherproof (locks from inside) but prevents thief from using credit card to lift the "U"-lock from outside the RV and walking inside. See ETEKJOY Flip Latch Lock on Amazon if you're interested in that.
