Generally, this message means that your certs/keys don’t line up with your CAs.
It’s not clear from what you provided what connection is triggering this message – unfortunately, the error message is generic to ANY SSL connection … more context would be useful.
You have observed that there are two separate sets of certs/keys/CAs … you need to make sure your client cert is aligning with the right CA – generally this will be the REST CA … but again, more context as to what is trying to make the connection would be useful.