Google Assistant suddenly cannot connect with a random device, breaking all interaction

I set up a year ago or so Google Assistant to interact with HA. It was a sound success and I could use my Google Minis to perform actions such as opening roller shaders.

Suddenly, a few weeks (?) ago , I could not manage to do that anymore, Google Assistant is giving irrelevant answers. When I say (in French)

open the rollers parents

it replies (also in French)

sorry, I cannot connect with the living room lights

The answer is always the same (incapacity to connect to a specific light area, namely “living room lights”), no matter the action I want to perform.

Both the rollers and the lights area work fine from within HA and I did not make any significant changes in the meantime (except for upgrading HA on a regular basis).

My main question is: has anyone seen that crap happening with their setup? And if so did you manage to fix it?

Subsidiary questions would be

  • any ideas what to look at to debug this WTF?

I will ultimately remove the integration and its presence in Google console and redo everything but I really would like to avoid this step.

I seem to remember having seen a similar topic somewhere (or rather the exact same) but cannot locate it anymore.