horizontal colored lines appearing after saving a PSD in PS

Well, it shouldn't be too difficult to test? Save local for a while.

Working directly to an external drive is not recommended and never has been. It's just a bad habit. Adobe officially warn against it. Yes, it may work perfectly for a while. And then one day it doesn't.

I constantly work on an external SSD so I wouldn't know. The SSD seems to work fine though. One more detail: while working on a photo, I save. But this issue occurs only when I save AND CLOSE the file.

@Diamantis23750061658e does the same thing happen when saving local? Drives can go bad

Same thing happens to me but only the last month or so although I've been directly working and saving to an external ssd for years now.

That's the kind of thing that works until it doesn't 😉

@Kevin Stohlmeyer i'll try doing so from the next project on. but i've been saving directy to external drives for years with no issues

@paolofus what happens if you save to your local drive? Saving directly to an external is not a supported workflow for Photoshop.

it happens when i'm closing the file and saving. as soon the file is saved, it appears with a line wherever you open or preview it

At what precise moment does this appear? When you are flattening? When you are saving? When you are reopening the saved file?

Are you saving directly to the external drive? That's not recommended. Save locally, then copy over.

I agree that it looks like file corruption, but determining where the corruption happens can be difficult.

it's an external ssd drive. i run a "s.o.s." utility disk diagnostics on it, with no negative results