can't parse Authentication-Results

[Alex <mysqlstudent@xxxxxxxxx>]

Hi,
I've just set up openarc on fedora38 with postfix-3.7.9. I believe it's
working properly, but I have a few questions.

I'm seeing messages like this periodically. I've found another similar
report from 2020, but there was no answer. Is there anything I could do to
fix this?

Jun 22 10:26:23 cipher openarc[2722824]: 394C41AF65537: can't parse
Authentication-Results; ga.mta1vsmtp.cc.prd.sparkpost smtp.user=<hidden>;
auth=pass (LOGIN) ; ignoring

It also appeared opendkim had some difficulty with it:
Jun 22 10:26:23 cipher opendkim[1313]: 394C41AF65537: failed to parse
Authentication-Results: header field
Jun 22 10:26:23 cipher opendkim[1313]: 394C41AF65537: DKIM verification
successful

Here are the ARC headers from a copy of this message delivered locally.
example.com is my domain. Does this look correct?
Authentication-Results: cipher.example.com; arc=none
smtp.remote-ip=209.216.NNN.114
ARC-Seal: i=1; a=rsa-sha256; d=example.com; s=default; t=1719066383;
        cv=none;
b=i54RBuHY9vEVutP/vW2HF76At9HhPLf+B/Ar6vXI5yiUz4P01Hlfs1pkEWHFlJu7BzrO3sei5aD+ekAvjZPO+qWs/aiQjMm8BOea0SypyFxSbR3+J9/2iAlZK/lzDkKhKYSNl3wJaCYBYqJ+xm/F3E/YPnj1RuzDws/wK4vcVGE=
ARC-Message-Signature: i=1; a=rsa-sha256; d=example.com; s=default;
        t=1719066383; c=relaxed/simple;
        bh=YzuX8fQaNPHchp5ri7UBPGzo95r7GvWiHsSC38CA/d0=;
        h=DKIM-Signature:Date:To:From:Subject:Message-ID:MIME-Version;
b=qtcIOvOXG0bPmC8uTQ5uoOvWri4P4klBCaKWoskZXNl6o/RR8WePsc5d28ZCiyGKd6sL0X3+5JztSBue3yBFkTByZvHUJc1ORDqdDQGguYvnHTC2wPfota4AQl6uFC2tBIRz9jLhcYqzvMMoA1cNtD/ZqQaZ+hT+xFRPSetuKFk=
ARC-Authentication-Results: i=1; cipher.example.com; dkim=pass (1024-bit
key, unprotected) header.d=thermostatsolutions.com header.i=@
thermostatsolutions.com header.a=rsa-sha256 header.s=scph0416
header.b=ATnXmMpK

Here is my config:
PidFile                 /run/openarc/openarc.pid
Syslog                  yes
UserID                  openarc:openarc
Socket                  local:/run/openarc/openarc.sock
Mode                    sv
SignHeaders
to,subject,message-id,date,from,mime-version,dkim-signature
PeerList                /etc/openarc/PeerList
MilterDebug             1
AuthservID              cipher.example.com
Canonicalization        relaxed/simple
Domain                  example.com
InternalHosts           /etc/openarc/TrustedHosts
KeyFile                 /etc/openarc/keys/example.com/default
FinalReceiver           no
Selector                default

I'm also trying to find a way to log more info in syslog about each email
it signs, but MilterDebug produces way too much debugging info to be
helpful. Is there a more verbose regular logging mode?