>>> "SM" == Stefan Monnier <monnier@iro.umontreal.ca> writes:

> Please make it a `M-x report-emacs-bug`.
> The problem is that the register you saved contained a string which
> contained some text properties whose value cannot be printed in
> a readable way.  The register code should catch the problem
> when writing the file (e.g. by stripping this property).

I see. What is not clear to me is why these text properties information
gets saved at first hand. I thought it might have to do with emacs
saving mechanism. I recall that saving registers did not cause any
problem, say in GNU emacs 26 (if I recall correctly).