recently i took come pictures with my (old) Powershot A640.
Most of them were fine, but on a pair of them i have some strange pattern on the right side of the image. I remember this happened few times also in 2012 or so.
You can find raw (with CHDK and converted with DCRAW) and jpeg file on this link on wetransfer:
What could it be? Better seen at 100%, on the right side.
Next shots were ok.
Thank you in advance.