How to fix
Hi everyone, a few months ago I had the same problem you are all having, with the mostly x axis vibrations and some on the y. Calibration, cleaning, and many other so called fixes did not work for me either, and I found only one root cause as well as a permenant fix.
Now these fixes are not for the light hearted, however this was the way I was encouraged by a Bambu lab support representative.
The Fix
In short, I needed to fully disassemble the tool head, in order to get a good view of the bushings. On my model, the x axis carbon brushings were brass with the carbon brushes exposed, these are not directly connected to the tool head but held in place with 4 springs. It is possible and it was the case with me that these springs were pushing in the brushings, causing extra friction on the x axis, leading the vibrations, which eventually ended up scratching the rods, it just happened over time that I didn’t realise these scratches.
So I showed Bambu support all of this evidence, and because I was in warranty they sent a replacement x axis gantry. This was hard to replace and involves lots of work with belts and taking off all panels etc…
I decided to have a look at the brushings on the new unit and it turns out that they were protected with a stainless steel sleeve, so thus meant the brushings were no longer exposed and could not be damaged by springs pushing in over time. I have had this replacement x axis for about 6 months now and have had no problems.
I will only recommend disassembling the tool head if you are confident as well as using the guide online.
Hope this works for you guys and has helped.