Error: stdout:
stderr: R4****: ambiguous (matches "iPhone Developer: Iron (R4G****)" and "iPhone Developer: Iron (R4****)" in /Users/eh/Library/Keychains/login.keychain-db)
If you trying to sign a app using applesign or objection and getting the above error, then it can't sign as there is a cert for iOS developer and Apple developer in the keychain, revoke all unnessery certifications from the developer.apple.com and then from the keychain.
Verify what certs you have with security find-identity -v -p codesigning