Comma in Content Causes Empty 'result' Array in JSON Response

The actual DNS record I’m having issue with is a lengthy DMARC record, but for simplicity, assume I have a DNS record whose type is TXT, name is text and content is This text doesn't contain a comma. I can get its details using:{zone_identifier}/dns_records/?type=TXT& text doesn't contain a comma

If I change its content to This text contains, a comma and attempt to get its details again (changing the content parameter appropriately)…{zone_identifier}/dns_records/?type=TXT& text contains, a comma

…the JSON response contains an empty result array:

    "result": [],
    "success": true,
    "errors": [],
    "messages": [],
    "result_info": {
        "page": 1,
        "per_page": 100,
        "count": 0,
        "total_count": 0,
        "total_pages": 1

The type, name and content params are URL-encoded in the request (, = %2C), so I can’t understand why this is happening. I could get the record ID using only the type and name params, but it’s possible (but unlikely) there is more than one record matching that criteria.

Any insights would be gratefully appreciated.

Thanks, Steve.