Repairing a Fabia Aerial

This morning I found my aerial by the side of the car.  Looks like it was pulled off.
Given that it's a bit chewed I'm thinking a fox did it.  We have lots around here.

There is a metal "plug" that the aerial screws into which looks like it just pushs back intto the roof unit, although I can't see how it is retained other tham by the rubbery surround of the roof unit.

I pushed the plug back in and threaded the aerial back on.  I can get AM and FM but not DAB.
Looking into the hole the plug came out of I can see a circuit board but can identify very little.

Should there be a way to retain the plug into the roof unit?

Is there some sort of connector in the roof unit that I need to align with the plug?

Thanks for any advice.