Is it a recent regression of your LilyPond package for macOS?
I’m afraid that question doesn’t have much meaning either: this packaging is newly developed, so there’s nothing to regress *from*. What I can tell you is that it consistently affects one user (and, I believe, on all builds I’ve so far done with this method), but everyone else has no problems with these builds, and the user who *is* having problems was able to run the 32-bit Mac builds, but those are built by a somewhat different process.
I know this information is less helpful and comprehensive than we might like, but since I’m still developing this particular build and packaging process, there’s very little to go on.
Unfortunately, Guile 1.8 has been unmaintained for several years and its
code base has almost nothing in common with that of 2.0 and later, so I
won’t make any promises.
Understood. Believe me, if I could upgrade to a recent Guile, I would, but my objective here is mostly to get a working 64-bit Mac build of LilyPond while changing the code as little as possible. :)