Hi,
Just wondering if you filter your formula before putting it through the lact aid? I found several times that the tube was blocked if my DD wasn't getting enough milk. Someone suggested that I filter the milk through a wet paper towel first, then through the lact aid filter. I found that alleviated almost all the issues. Every once in a while, I would give a test suck on the tube to make sure it was clear.
I would try and use the lact aid as much as possible instead of the bottle. The later is easier and can be preferred in a very short period of time for a NB