OWASP Rule Groups Blocking Legitmate Requests

you need to check the http request body because the error log said this:

=========

...

"terminatingRuleMatchDetails": [
{
"conditionType": "REGEX",
"location": "BODY",
"matchedData": null,
"matchedFieldName": ""
}
],

...

=======

you can use tcpdump to capture whole packets
tcpdump ... -s 0 -f5 ssl