xf18 1.4 XF18mm 1.4 on a XT4 full spectrum suddenly not focusing

[Edu]

After a few years enjoying the perfect combo of the XF18 1.4 on a XT4 Full Spectrum converted, it suddenly stopped working.

I have basically used the combination to take landscape photos and infrared videos, and they have always given me spectacularly sharp results with no focus problems, even in automatic mode.

Suddenly, one day (I don't remember if there was a firmware update in between), the focusing distance was reduced to a few meters... making it impossible to focus at infinity (not even manually).

I took the camera to have it "repaired", but they said it was fine. The 18mm works perfectly with my XH2. So... what am I missing? I have done all the tests that were and are possible with my knowledge.

Any ideas?

Edited October 20, 2024 by Edu
Forgot tags

[pw-pix]

Do you have a different lens to test on the modified X-T4 to see if it is the camera body causing the problem?

Have you cleaned to lens and body contacts and retested the 18/1.4 and X-T4 combo?

Have you checked to make sure there isn't some odd AF setting configured in the X-T4 body?

Accidentally gone to a bracketing mode (perhaps AF or focus stacking)?

What does the EXIF data show for the images where the problem occurs?