In case anyone else has the same issue we just encountered. We were using hyphens in the path param names (e.g. {organisation-id}) which is valid OpenAPI 3.0 but messes up preg_match (apparently you can't have hyphens in field names: https://stackoverflow.com/a/62207383)

This results in an error like:

preg_match(): Compilation failed: syntax error in subpattern name (missing terminator)
Unable to parse "#/organisations/(?<organisation-id>[^/]+)#" against the pattern "/organisations/{organisation-id}"

This comes from the parseParams method in OperationAddress.php