Headlights unevenly bright

[NSLIII]

I'm new to this forum so in advance thanks for any help.

Yesterday I changed the low beam halogen bulbs on my 2010 A4 B8 to a whiter Philips bulb. It seemed to work fine but I noticed in the reflection on cars in front of me that the left bulb (from drivers perspective) was slightly brighter than the right bulb.
To exclude the bulbs as the cause I changed the bulbs back to the original ones that used to work without a problem but the issue persists. I.e. the bulbs aren't the problem.

It feels like something went wrong with the taking out and putting back in of the headlights. To be clear, it is not that the right bulb hardly gives off any light like you sometimes see on cars. It is properly on but still noticeably less than the left bulb. The daytime running lights and high beam seem unaffected.

Do I need to go to a garage or could I try something myself?

[Lambda13]

Have you tried flipping the bulbs to the opposite sides to see if the bulb is just weaker?

[NSLIII]

I have even tried multiple bulbs that show the same issue so I can safely exclude the bulb being the problem. Because the difference is slight I was hoping it would be a alignment problem. Tonight I put the car in front of a wall to align the headlights with the white plastic screws but I can still notice the same problem. My feeling is that it has something to do with the reflector because it could be that the lamp is actually outputting the same amount of light. I noticed that when I put it in front of a wall, the left light is more concentrated and the right light more scattered.