[1.6.7] Weird Magical Combat bug with Adventurer

[Horken]

Adventurer built to maximize the number of procs of arcane combat:
-knives, in particular fan of knives
-tentacle hand
-flexible combat prodigy
-arcane combat set to lightning
-psionic wielded weapon (but this is probably irrelevant)

Sometimes multiple lightnings would trigger, visually appear to hit the target, but do no damage as seen in the combat log. I attached screenshots of the combat log:
-first screenshot: lots of melee hits on the target, lightning triggering, but no corresponding lightning damage (from the triggered spell, lightning on melee hit did happen). The searing light proc form the gloves did do damage (it is in the fourth knives hit)
-second screenshot: everything working as intended, with a similar hit but the damage happening.
-third screenshot: this is possibly unrelated, but once in a fight I ducked back across a corner and waited for the rare to come into view again, and when it did random lightning casts triggered visually and appeared in the log, but there was no obvious cause and no related damage.

Some comments:
- The bug was quite rare, but when it happened, it would happen repeatedly against the same monster
- Possibly, me or the monster moving would fix it
- I had the impression that the bug happened more often with alchemist gloves, but I quickly changed to other gloves, so I am not sure.
I did check that the bug could happen with me not having any ice damage, just to make sure that it is not some weird ice block interaction.
- If you check the combat log, when the bug happened there where no melee critical strikes. When the bug did not happen, there where lots of melee critical strikes interspersed with the lightning triggers.