I have solved the issue on my side. Did some "file re-structuring" with NMG's scenery installation. Replaced their new APX56420.bgl file in ...\Scenery\0705\Scenery folder with the original default APX56420.bgl file to get rid of the duplicate fale afcad. Deleted AFX_FALA_ALT.bgl added by NMG in ...\Scenery\World\Scenery folder and fala-approach.bgl file in ...Nmg\Fale\Scenery. Now GSX reads the correct NMG fale-afcad file and working fine, again.
I must emphasize, this solved the issue on my installation, I fly online mostly and do not use any AI traffic.
Johann