asking from pure ignorance: what does that mean in practice? did you lost your funds? can't route any other payments? Can't receive them?

They all are

There is always a risk when having fresh channels on core lightning (Blockstream)

Time to switch my friend! try https://github.com/lightningdevkit/ldk-server

Is this condition confined to your CORE lightning node? Is there a widespread problem?

Ah, good luck.

Lightning is a difficult world This has happened to me a number of times with lnd, but I think it's mainly a lack of TLC on my part that caused it. Experience helps make living with lightning 'safer'