No--if you never manipulate the individual bulbs directly, I don't see much use in trying that. What I meant is to manually try what you've said your automation is ultimately doing: manipulate the group device (turn it on and off a few times yourself) and see if you can replicate the problem you see when you use this group device in an automation. If I understand your problem correctly, it's that your individual devices do not always respond when your motion lighting automation manipulates the group device. Because the the on/off state of the group device always appears correct, the problem is likely not your automation (it must be working if those are right, and the problem must lie with something--whether something you can control or not--in your group). My suggestion is just one way to take the motion lighting automation out of the picture and test this hypothesis. Correct me if any of my understanding is wrong about your actual problem (but the takeaway is that Motion Lighting seems irrelevant).
This isn't really relevant now; I was talking about what staff have mentioned may be coming in a future version of Groups and Scenes.
When testing this (or testing a real automation, ideally one at a time), I'd highly recommend you check your "In Use By" for all devices (both the group and the individual devices) to make sure no other app/automation might be touching them. You can temporarily disable apps if needed (see: [TUTORIAL] How to disable Apps and Devices (platform v2.0.3 or newer)). You definitely need to make sure no other automation is interfering with this one and changing devices in ways you did not expect that might lead to this problem; disabling any other one that touches the device (and maybe all of them when you perform the "manual" test I described above) is a good way to do that.
Switching out a Hue bulb (assuming it's a Hue Bridge bulb or that you have no other kind, i.e., non-bulbs, of Zigbee devices on your network) would be one way to see if it's something with a Yeelight just not receiving a command or if it's something with the automation(s). Now that I mention that, turning on logging (default info/description logging might be enough--probably don't need debug, but it can't hurt) for your individual bulbs might be a good idea too so you can see what they think they're doing.
