Where to go next with you GO 550...?

You could try running clearflash.exe 3 times from [Only registered and activated users can see links. ]

Re the mapsettings.cfg, this is only saving previous settings like recent destinations, sounds, voices etc but some find deleting this file can help (although as you say, there wasn't one initially anyway)

If F/A created a dct it must have found your ttgo.bif and you say your navcore is deffo patched already

Soooo.... either ALL the maps you're trying are incomplete/corrupted/nested or your navcore 9.510 is incomplete/corrupted.

Sorry to "state the bleedin' obvious" but it has to be one or the other.

How about grabbing a clean copy of the official 9.510 from [Only registered and activated users can see links. ] then copy/paste/overwrite onto your root then run F/A option 3 to patch it