bug#62216: Narrowed the issue to one line

[Paul Eggert]

On 8/22/23 10:41, Eli Zaretskii wrote:
> > Possibly the problem has to do with markers pointing into the buffer, so
> > it might be helpful to log their contents before and after the insert in
> > question.
> Can you elaborate?  What kind of problems could the markers cause in
> this case? disrupt the character-to-byte position conversion?
> something else?

Not really. It's just a wild guess. I haven't looked at the code in detail.