It got corrupted twice today, but lucky enough I could fix it in both occasions. But the strange thing about it was that in on both occasions the exact same beveled corner brick got replaced with, believe it or not, the same 1/4th circle segment brick on both occasions. This basically rules out that it was due to a accidental manual swap on my behalf, but rahter at random. After I restored it again I decided to make a backup clone of it!

Somehow this clone seemed to be currupted right from the start, and, yes, in exactly the same way again.

So, I fixed it again, this time not brick-swapping, but brick by brick manually, and each time the brick was freshly taken from the standard brick pallet rather than the custom pallet, hoping to eliminate whatever traces it left behind completely. So in the process I also automatically replaced possible rotated duplicated with its original correctly positioned variety. when I completed this task I pressed "Shift+T" as well, to Remove unused, duplicate and empty Palette Slots. 

But still something within the font is keeping some sort of traces for this bug.

Any one got any clues?

And again the same thing happened after saving the font again, so restoration once again. I just completed another manual brick by brick cleanup for all affected glyphs. Same as I did with the backup clone, which is replacing every possible rotated copy of it with a freshly recomposited and propper orientated variation. Lets hope it was the last time for it to occure, because this has me pretty scared of any any changes to the font all together right now!

Okay, I think I effectively canceled out all the conflicts that caused the font to corrupt upon saving. Seems stable again right now. (multple saves done without corrupting it again so far!!)