Some portals continue to look like they have frackers on them well after the frackers have burned out. It’s okay though, NiaOps is all over it:

Agents, we've confirmed reports of unintended and erratic Portal and Fracker behavior. We are actively working on resolving these issues and will report back once we have more information. Thanks for your patience.

— Niantic Support (@NianticHelp) March 4, 2019