Thanks @MaciekB for your question. Please review details of BUG-000157157 and confirm if that is what you are experiencing?
What else to check:
1. Check if strings for the road label are derived from two or more fields
2. Check that all road features have both fields values populated (not Null)
We fixed this issue with ArcGIS Pro 3.2 release. Are you able to upgrade to this version even if only to test?