Observed in 2.3.1:
It seems using --clearsign creates some memory corruption. To reproduce, set MALLOC_CHECK_=2 and (probably not required) MALLOC_PERTURB_=21 before running the test suite. First failing check is <standard>/ tests/openpgp/clearsig.scm.
The error is most likely triggered in the final xfree (afx); statement in armor.c:release_armor_context. I have no reason to assume this was fixed since the 2.3.1 release.