Zigbee sensors become unknown when data value is "null"

[brjhaverkamp (Bert)]

Hello all,

Since a few weeks (maybe longer, as I wasn't paying much attention) my zigbee temperature sensors that are connected via zigbee2mqtt(z2m) are intermittently "unknown" in my dashboard.
When I open the sensor to look at the graph, I see a sort of speckle line, the sensor values are reported regularly, but there are blank spots in between.

When I look in the z2m logs I see my sensors (not just the temperature sensors) are reporting the value "null" regularly, and sometimes a real value. I notice that everytime z2m gets a "null", the sensor switches to "unknown" in ha. This is not just on one type or even one brand of sensors. It is on all of them.

I've looked at interference but the LQI values are good. What can be going on here?
And has something changed in the recent months? Those sensors have worked perfectly for years. Any help/hint is appreciated.

Regards,

Bert

[Sir_Goodenough ((SG) WhatAreWeFixing.Today)]

1. Are there ANY zigbee routing devices in your network that are physically switched on and off (power cut so they go dead)?
2. Do you have enough routing devices?

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[brjhaverkamp (Bert)]

Yes, I have 7 routing devices. Only 1 of them is a "switched" device, a lightbulb but it is always on. (I hid the switch:-)
Only a few devices have a LQI under 50 in the z2m overview

I am really at a loss.. I feel I checked about everything. I removed and repaired multiple times with multiple devices. I put the coordinator on a different usb port, on a longer cable.. to no avail.

Any suggestion is appreciated

Bert

[ShadowFist]

@brjhaverkamp

Yes, I have 7 routing devices. Only 1 of them is a "switched" device, a lightbulb but it is always on. (I hid the switch:-)
Only a few devices have a LQI under 50 in the z2m overview

Ok, but are the sensors actually routing via the routers, or are they trying to speak directly to the coordinator? You can check this in the zigbee map.

Note that some older (zigbee 1.2) sensors will not try to negotiate a better route, so if you paired them directly to the coordinator, they'll try to communicate with it directly despite better routers being present.
You can work around this by pairing the sensors via the closest router - there's a small arrow next to Permit Join in Z2M which allows you to select any router via which sensors can be paired.