Strange lines down centre of some scans

Just recently my elderly Epson V-series scanner has started doing something strange. The last three films I've scanned have exhibited these lines down the middle of some, but not all, frames. The affected films were shot in different cameras, and I cannot see anything on the negatives.

I've tried cleaning the glass. Could there be something inside the scanner? These lines are coming out dark though, surely some grit in the optical path would come out white/light?

I did try rescanning the affected images at various resolutions and got the same result. But it's very odd as some negatives in the same strip are perfectly fine.

I've attached two recent examples.

Agulliver said:

Could there be something inside the scanner?

Click to expand...

There are 4 glass surfaces involved in scanning film on a flatbed like this. Top and bottom of the transparency lid glass, and top & bottom of the platen. You need to (eventually) clean all 4 surfaces.
The problem you're running into may have to do with dust in the calibration area, so the strip closest to the head parking zone, nearest to the lid hinge.

Agulliver said:

But it's very odd as some negatives in the same strip are perfectly fine.

Click to expand...

Yes, that's odd; stuff in the calibration area tends to end up in all frames on the same strip/line.

Maybe a little dust on the scan head.

I guess I might need to figure out how to clean the internal glass surfaces.