A rare bug in One UI (Samsung's software) or an outdated system can cause call handling to malfunction.
Sometimes the block isn't on your Samsung device at all. Your mobile carrier may be blocking the number due to its own spam lists or a feature you enabled (e.g., Verizon Call Filter, T-Mobile Scam Shield). samsung blocked call
Bug Report: Samsung "Smart Call" Feature Blocking Safe Contacts A rare bug in One UI (Samsung's software)