Panel displaying "plugin panel not found: undefined" in public dashboard mode

I’m running Grafana 9.1.6 on a Windows server in an Intranet setting.

I have a few public dashboards setup which work fine, except for a couple of panel instances which display an error.

I am using the Time Series plugin in multiple panels on the same dashboard. The panels are all the same, except for the query parameters used to pull out the data.
In non-public mode, all the panels work perfectly.

If I view the dashboard using the link in the public dashboard setting, one of the dozen or so (almost identical) Time Series panels displays the text “Plugin panel not found: undefined”. It happens to be the first panel on the dashboard.

I have been experimenting with the Dynamic text panel as well, which I have linked to an rss feed. This panel also displays the same text in public dashboard mode. It works fine in non-public dashboard viewing mode.
As an experiment I added a plain Text panel with some text. It displayed correctly, so its not an issue where all new panels which are being affected.

I am at a loss as to how to diagnose this issue. Obviously the panel plugin can be found because I have a dozen copies of the time series panel on the same dashboard.

Any suggestions as to a fix or even what I can do to diagnose this problem?

If this is of any help, grafana.log displays logs like this whenever a public panel updates

logger=context traceID=00000000000000000000000000000000 userId=2 orgId=1 uname=kiosk1 t=2022-10-10T11:03:40.5419253+02:00 level=error msg=“Query data error” error=“plugin unavailable” remote_addr=10.2.100.123 traceID=00000000000000000000000000000000

I also see regular logs with the following:
logger=context traceID=00000000000000000000000000000000 userId=0 orgId=0 uname= t=2022-10-10T10:49:56.0599547+02:00 level=error msg=“Error from access control system” error=“no resolver found”

which don’t seem to occur at the same time as the previous errors. However, I only have 2 kiosks set up, pulling from the same data source, and a single admin account, so the sources of these errors are limited.
Any idea why the access control system would be generating a ‘no resolver found’ error? I only use a couple of internal user accounts - no ldap, no external authentication.