Group Helper On/Off Unreliable

I’ve tried to find an answer to this to no avail…

I’ve recently started converting my small number of IKEA bulbs and “drivers” (their term for their connected cabinet light power sources) to ZHA (via ConBee II stick). I wanted to add non-IKEA Zigbee stuff to my home anyway and wanted a single platform; I also disliked their need to use a “steering device” (remote) to deal with things. The conversion itself has been easy, and has gone well.

EXCEPT… When I create a Group Helper so I can control a pair of IKEA bulbs as a unit, the groups are unreliable. If I turn the group on (or off), there’s a 50/50 chance that both bulbs will actually go on (or off). Sometimes they do; more often, one of the two bulbs doesn’t respond.

I’ve created two Group Helpers, each with two bulbs in the group, and both of the groups behave exactly the same way. I’d like to just add a slight delay to see if it helps, but see no way of doing that, unless I’m missing it somewhere. But I also don’t know that I grasp why it’s doing this to begin with.

Any insight or help would be appreciated.

Further: It appears that creating the groups within ZHA itself, vs. using Helpers, is an answer to this. If someone can explain why I might do one vs. the other, I’d love to understand this better…