LwM2M: disconnected LwM2M devices constantly display as active with lastActivityTime always being very recent

[alanthompsonch]

Describe the bug
Registered LwM2M device shown as active with a recent lastActivityTime and lastConnectTime (2 minutes ago at the time of writing this), although it has been disconnected and without batteries for 6 days.

Your Server Environment
own setup

Deployment: monolith and microservices
Deployment type: deb and k8s
ThingsBoard Version 3.6.3PE and 3.6.3CE
Community and Professional Edition
OS Ubuntu LTS

Your Client Environment

• Windows 11
• Firefox
• 125.0.3

Your Device

• Connectivity
  • LwM2M
  • CoAP

To Reproduce
Steps to reproduce the behavior:

1. Register LwM2M client device
2. Let it send some data
3. remove batteries
4. wait for lwm2m lifetime to expire
5. wait for a while longer if you like
6. See that the device is still shown as active and that the lastActivityTime and lastConnectTime are very recent

Expected behavior
lastActivityTime and lastConnectTime should be way older and not constantly refresh to current values and device should be shown as inactive

Screenshots