ᐅ Gap between garage frame and stainless steel lintel – flexible sealing

Hello everyone,

Our garage was completed in 2019. A 6m (20 feet) wide Hörmann garage door was installed. The upper fixed frame was attached to the inner concrete lintel using steel brackets (see photos).
Between the frame and the front stainless steel lintel, a type of compressible sealing tape was applied to seal the gap there. When closing the door, this sealing tape is especially compressed in the middle of the door because the door pushes the frame slightly outward. When opening the door, however, the sealing tape doesn’t relax enough, causing a gap to form between the frame and the stainless steel lintel.
Currently, it appears that even when the door is closed, there is still a certain gap through which air constantly flows, which depending on the weather, causes (moisture-related) problems.
The garage door installer usually secures this frame to the front lintel with screws. Since our lintel is stainless steel and therefore difficult to drill into, he used Hörmann mounting brackets instead. In his opinion, this gap could now be sealed with silicone. I am unsure whether silicone is the best choice here.

In my view, the challenge is that the gap regularly “moves.” Is there a specific solution for sealing a flexible gap like this? What do you recommend for this situation?

From experience:
It should not bulge outward; either the built-in component or the masonry does not fit properly.
As a solution, I am considering Sikaflex.