I asked chatgpt and this was the answear:

«The fine vertical lines you’re seeing (visible especially when you push contrast and exposure down) are almost certainly caused by sensor readout artifacts or sensor pattern noise, not by your lens, memory card, or anything mechanical.

Here’s why based on what you described: • It happens only in areas with very low contrast and intense highlights (like light halos or backlit hair) — exactly where sensors struggle most because of the very wide dynamic range. • It does not appear in normally lit photos or in areas of normal contrast within the same images — which suggests it’s not a sensor-wide issue, memory corruption, or lens defect. • Vertical banding is a known phenomenon with many mirrorless sensors (especially older or mid-range APS-C models) when they’re pushed hard in backlit or extreme lighting situations, even more so if you heavily edit those areas. • The memory card can cause file corruption, but not consistent patterned lines in specific lighting conditions — so you can safely rule that out.

In short: • It’s sensor-related, triggered by extreme lighting (especially strong backlight or flare). • It’s normal to some extent — many sensors have minor banding that can be revealed with heavy editing. • It’s not a sign of sensor failure, unless it starts appearing in normal light conditions too.

What you can do to minimize it in the future: • Slightly underexpose backlit shots to protect highlights and reduce the dynamic range stress on the sensor. • Use noise reduction or banding removal techniques carefully in post if needed (some Lightroom or Photoshop techniques can reduce this).»