I’d verify the DTHs are local first in the IDE under devices in the top menu. (u may have to click on locations first and choose your location name, then you can choose devices from the top links) Then check the distance between the hub and each device. These devices use different wireless frequencies to communicate, zigbee and zwave. Depending on what order you’ve paired the zwave devices to the hub, the switch may be a repeated mesh signal. The zwave frequency is closer to 900Mhz so cordless phones, baby monitors etc can disrupt. While the zigbee frequency is in the 2.4Mhz band, same as most home WiFi frequency. I would move the motion sensor closer to the hub and retest. Also a falling or defective battery can cause intermittent issues.
Your zigbee device may have newer versions of firmware that improve mesh and radio communication. You can enable live firmware updates in the IDE.Discussed in this thread, basically hubs/utilities/enable ota.
You could also check the live logs while testing. That way you can see the failure point. For example, you should see the motion sensor report active then smart lightning app send on command to light switch and then the switch report on. The live logging is in the IDE is also in the top menu. It starts showing the log after you load the page and things happen like motion active etc.
There can be many different things that cause this, and you may be running into several of them, or different ones at different times.
@Matt_Behnken already detailed several possibilities, let me just toss out a few more.
One of the most common in the setup you describe is that the motion sensor, which is battery-powered, was asleep when you first walked in. (No, really–it’s a “sleepy device” to conserve battery life.).
It can also have to do with motion sensor placement.
I’m not feeling very well today, so I’m not going to go into a lot of details, others can cover any follow up, but the point is just that motion sensors themselves can be tricky.
One other question: do you have any zigbee bulbs connected directly to the SmartThings hub? (Not to a hue bridge.) I understand you are trying to use the sensor to turn on a zwave switch, but I just want to know if there any bulbs that the sensor might be trying to use as a repeater.
Also, when is the last time you ran the zwave repair utility and what results did you get?
The point of these two questions is that if the sensor has multiple paths to the hub, or the hub has multiple paths to the switch, it may be that some of those paths work better than others. So it could be that if the efficient path happens to be busy at the time that you walk into the room, the message is getting routed along an alternate path that doesn’t work as well. This kind of thing is a common reason for inconsistent performance in a mesh network and in this case you are dealing with two different mesh networks.
If none of the suggestions brought up so far seem to help, the next step I’d do would be to try to determine where specifically in the sequence the lag had occurred. Did the sensor fire and there was a lag before the light came on? Or did the sensor fail to fire? Or did the sensor fire but the message didn’t go through?
Again, I’ll leave the details of how to do all that to other people for now.