I've just published fixes for errata for SRFI 224. They have been submitted by the author, Wolfgang Corcoran-Mathe, so I have incorporated them into the public document and added a note to the Status section.
Here are Wolfgang's comments on the fixes:
[This] fixes an omission in the spec of fxmapping-alter described by John in https://srfi-email.schemers.org/srfi-225/msg/17591444/.
Here's the diff:
https://github.com/scheme-requests-for-implementation/srfi-224/compare/errata-1^..errata-1
Regards,
SRFI Editor