Back on the subject of water leaking into the indicator units (better late than never), trying now 6 units, 2 new, I am 100% certain that it is the rubber seal which should get compressed to seal when the bayonet fitting is pushed and turned to lock it. The problem appears to be that the seal goes "sloppy". A new one barely turns on the lamp holder. Used ones have lots of play and feel, well, 'used' ! The inner diameter no longer grips onto the shaft of the holder and the outer diameter has spread (almost 2 mm). Anything such as silicon grease or Vaseline, which both can cause extra swelling, just makes matters much worse.
Since the rubber seal appears not to be available, it is indeed a matter of new units, at least the bulb holder/seal part, or drill the holes like Bainzi says. Maybe both !
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