Many months ago, I encountered errors a number of times when switching between Orbx’s NA and AU regions with FTX Central utility.    Since then, I started using the following approach:

Whenever switching from NA region to AU region or vice versa, I will switch to Default FSX region first as an intermediate step.

With this extra step, I have never encountered any problem again from switching regions.   This is particularly important for my multi-flying zone setup.