You think you have seen it all with electricity?

Yes - that link as shown in #2 works fine!

I've come across this problem before, after one of our labs was re-lamped with new T-8 fixtures, with electronic ballasts (7 4' fixtures on each row; 6 rows) 347V. The contractor had mixed up the regular house power lighting neutral with the 'emergency' lighting neutral, which are supplied by separate transformers.

The funny thing was that the effect was intermittent, as most times the lights worked fine, however, every once in a while the same disco floor flashing would happen, leaving us scratching our heads, wondering what was happening.

After detective troubleshooting, we split up the mixed (crossed) neutrals to their proper assigned fixtures, and that fixed the problem. Hope this helps for your situation - Loupy.