[Evolution] Sometimes can't verify signature

[jeff vanepps gmail com]

Evolution is able to verify the gpg signature on some messages but on
other messages it says "Error verifying signature: Failed to execute
gpg." I have not been able to get it to tell me any details about the
error. When I run

CAMEL_DEBUG=all evolution > foo.txt

the resulting file does not contain "gpg", "Error verifying signature",
or "Failed to execute gpg". It does contain "GNUPG" in two places which
both only say

status: [GNUPG:] NODATA 4

Is there a way to get it to output the actual gpg command it is
executing and the output from that command?

Also, I don't see a way to export the signature, just to help me
investigate (no attachment bar or anything). Is there one?
(FYI: Content-Type: multipart/signed; micalg=pgp-sha512;
protocol="application/pgp-signature"; )

Evolution 3.34.1-2

(Thunderbird/Enigmail verifies the signature no problem)