I just bought a house that has a two-year old Carrier central air/ furnace unit. The filter holder slot has a convex bend on the side closer to the furnace which makes little gaps between the filter's cardboard frame and the metal filter holder. When the fan is running I can feel a little air flowing into these gaps rather than through filter.
Here is a picture:
I'd estimate the top gap is less than 1/8" and lower is maybe 1/4". This does not change when the fan kicks in, i.e. neither the filter nor the metal frame flexes to close the gap. When the fan is running I can feel a small amount of air flowing into the gaps, which would obviously not be getting filtered.
Is this a big deal? I assume like 95%+ of the air coming in the main return duct is flowing through the filter as intended, not flowing out around it and into those gaps.
Is it worth trying to bend the right side of the frame to be more flat, or having a service tech in to straighten it?
Note that there is no door that closes to cover the filter slot. It's permanently open by design AFAIK.
Filter insertion area, filter removed:
Filter slot viewed from inside:
So the filter's cardboard frame roughly sits where these red lines are: