Federal Pacific Stab-Lok panels were installed heavily through the 1970s and they are still in service across older Ocala neighborhoods. The documented problem is breakers that fail to trip under overload conditions, which defeats the entire point of the panel. Zinsco and Challenger panels of the same era have their own failure patterns, usually bus bar corrosion and breakers that loosen on the stab.
There is no repair path. Replacement breakers for these panels are either unavailable or of unverified provenance, and the panel enclosure itself is often the problem. The work is a full changeout to current listed equipment, which in most cases is combined with a service upgrade because the existing service is undersized anyway.
Home inspectors flag these panels routinely, and it comes up at closing. If you are planning to sell within a couple of years, doing it now on your own schedule costs less than doing it during a contract.
Technician insight
A Stab-Lok breaker can look and feel completely normal in the hand. The failure is internal to the trip mechanism, which is why visual inspection tells you nothing useful.