Bad_ReadOnly when updating a UDT tag Value


When I try to edit some tag values that sit under a UDT within Designer I get an error Bad_ReadOnly popup. I’m puzzled what I’m doing wrong as some tags that sit under the same Edge Nodes but are not under a UDT can be edited (i.e. I can see Ignition issuing a DCMD message over MQTT).

I’m using Ignition + MQTT Engine. I create tags with the Node-RED Sparkplug client.

What can cause this error?
I’m running Ignition 8.1.



To add to this I’m able to system.tag.copy and the Read Only field is set to false by default.

I’ve tried 2 commands:
system.tag.writeBlocking([cmd_resp_path], ["Command Rejected. Permission Error"], 5000)
system.tag.write(cmd_name_path, "Command Rejected. Original Command")

The Legacy system.tag.write is the only one that gives an error: