"how do I unglue".

I don't, I cut. I use a new blade in a utility knife, same thing if I find strip edges out of alignment more than 1/64.

I've made every mistake, and after so many, realized just how much time and angst was wasted, when replacement was fast and much less pain.

I've had veneers crack as I put them down, and I'd think, that won't look bad, or be visible, and it was bad. Denial!

I put an off-color strip in the middle of a rear deck, and fought the devil on one shoulder and the angle on the other shoulder for days, until I just cut it out! Once I did that, I couldn't believe I even considered leaving it in place.

Hence my rule, if you even for a second think it might be bad, it is bad. Don't patch it, don't doctor it, rip it out and start over.

Once you work with that rule, you can fix anything, fast and happy results.

Rob