First of all, thank you very much for looking into this and helping me out. I'll try and answer your questions as follows:
Midi Setup: lately I use OnSong on iPad which I control wirelessly via MFC. A PC command is sent to the AxeFX which relays it to OnSong via MidiThrough which then calls a new lyrics sheet and sends a command to the AxeFx to load the corresponding preset.
When I first mused about this setup I thought that there may be room for occurring midi mixups. On second thought, though, I am positive that the 'uses global blocks' bug occurred way before I started using OnSong or the iPad. Therefore I tend to rule it out as the culprit.
Editors: I only use the front panel and AE exclusively. Oh, and FractalBot of course.
GlobalAmpBlock Reset: to be honest I wouldn't even know that such a function exists, therefore I'd say I've never used it.
Scene Controllers: there are no SC used.
Cc35/36: never used.
Manual block bypass: yes, i do use it, mainly by using a foot pedal or by switching scenes.
Voltage: should be no issue being in Europe. Never ever has.
Internal backup: I use this function every time after rechecking all presets and making sure they work all right. This is kind of my failsafe for a show - however, last time it didn't work since the bug persisted even after I restored the presets from onboard memory.
The preset was originally created several firmwares ago. However, since I had some problems with that particular preset before, I completely erased it using AE and built it from scratch on Q8.01. However, I had the bug occurring on other presets before, too, which have been originally created pre-Quantum and adapted since.
I hope this helps finding the source of the bug. Thank you very much.