Brainstorming something weird

A friend's guild mate reported that in one account Dash's basic was calling assists and in the other it wasn't They double checked and abilities were maxed and they had prepared allies. The obvious stuff was confirmed not to be the problem.

So we're just brainstorming ideas, like maybe the one that didn't assist was during an attack on Darth Revan or something? Then it occurred to us that neither of us has all the DataCron and Omicron abilities memorized, so we thought we would just come here. Before assuming this is a bug, does anyone have any ideas that would explain this.

So far all we've got are:
1) attacking DR
2) Conquest/Galactic Challenge Modifiers preventing assists?
3) Datacrons preventing assists?

Anyone got details on how this would happen? Or should we start looking at the possibility this is a bug?

ETA:

Unfortunately I cannot provide more details. (For instance against what enemies and in what game modes.) That was part of why I brought it here to brainstorm, because my friend is a guild officer and got this message which mentioned some of the usual suspects (like did he double check that he had his basic maxed) but far too few details other than that.

I'm sorry I didn't mention Deadly Bluff -- we did think of that, but I hadn't written it as a possibility above. To the people who mentioned it, you're right, that's a good thing to check.

one thing I hadn't thought about was that some teams gain effective crit immunity at the start of the battle. (e.g. JMK squads w/ bonus prot and SLKR squads with Advantage). That's something to ask about. Thanks, folks.

More ideas are always welcome.