Sealing a FFC ZIF connector
Hewlett Packard instruments in the 70's used to specify maintenance for their gold plated card edge fingers using only Pink Pearl©® Rubber erasers (lol).

Isoprop. does wonders with a Pink Pearl and the contamination could also include oil and water vapours which are excellent electrical insulators.

But the ZIF socket has a problem if the retention force is zero and does not have a "gas-tight" seal because even non-24 caret gold is still prone to some oxidation with high temp and humidity.

Examine the surface under a 10x lens and look for pitting and lubricate and wipe the mating contacts with isoprop and repeated Pink Pearl treatments to the FPC being careful not to leave any shreds inside the socket.

Then as @Almostdone has suggested use Plumber's waterproof stretch tape black tape for moisture leaks and wrap around the socket with minimal stress on the FPC yet sealing the clean surface with finger pressure after wraps.   

The alternative is  Silicone which still has moisture ingress but slows it down and  it may block greasy water vapours but may be harder to repair.

That should last you more than a year.  I wonder if Korean's use this microwave for Kimchi style cooking?  If so, Samsung ought to have a better Quality Reliability Test Engineers.



The other possibility is excess pressure on membrane carbon contacts has smeared the carbon to make certain buttons like "Start" wear out faster.