Custom cards work only until a page reload (when at all)

Newbie here - please forgive me if this is trivial, but after three days of banging my head, I am coming up with empty.

I spent the last few weeks setting up HA at home. I have all lighting, HVAC and the emergency generator hooked up, the Zigbee devices going through a Hubitat and its HACS integration and MQTT to talk to the Genmon instance monitoring the generator.
I have recently deployed Arlo cameras I got from a friend and had no problems with the AArlo HACS integration.

Where I am hitting a brick wall is with the UI.

I have installed the HACS frontend extensions Lovelace HASS Arlo, Canvas Gauge Card, Config Template Card and Button Card.
The aarlo-glance custom card contained in the Arlo integration is never picked up - it always returns an error. I tried all the solutions mentioned in the various threads and came up with empty.
The other ones are used for a complex card showing the generator stats. The card works perfectl when I create it, but it will fail at the first browser reload with the error “Custom Element does’t exist” for the config-template card.

When that happens, if I try to add any new card, the list comes up empty.

I am running Home Assistant Core 2022.6.7, Home Assistant Supervisor 2022.05.3, Home Assistant OS 8.2 on a Raspberry Pi 4B connected via ethernet.

Any help on how to debug this will be much appreciated. I would have to revert to a backup if I can’t get this fixed.