Automations with time triggers do not fire anymore

Hi, I'm looking for help about my C5 hubitat.

For several days now, every time triggered automation does not fire anymore, starting each night / morning. After rebooting the hub they fire up again at the right time all day long, until the next night / morning.

Before rebooting I checked the logs and the "faulty" automations : no particular issue in the logs (that I can see anyway) and every "faulty" automation is still scheduled as planned.

My free memory OS (RAM) is about 270000 when I check it.

Do some people already encounters this strange sudden behavior ? What did you do to resolve it if so ?

Thanks a lot.