I've noticed the same behavior and was able to resolve it by adding
--no-grafts whenever I reconfigure my system and home profiles. Likely
just the former is necessary, but I haven't tested it.
I've also noticed this behavior (SBCL trying to place .fasl in
/gnu/store) once when I pulled, reconfigured system, and didn't
reconfigure home. I have my setup configured such that StumpWM is
installed at the system level, while contrib packages are installed via
guix home.
I ran a git bisect and continually reconfigured my system to try and
narrow down what commit it was, and was able to isolate it to either an
xorgproto or Mesa update. Home was built before (49a7a95ba4) the commit,
System after (d55a4431f3). The offending commit in this particular case
lies somewhere between d55a4431f3 and 17c3a3bfff. (This probably isn't
actually a bug, but I'm posting it in case anyone else runs into a
similar issue in the future.)
If anyone else has a similar setup, encounters this issue, and already
uses --no-grafts, be sure both the system and home profiles are built
with the same version of Guix.
Richard Sent