Why does Jura F9 sometimes fill the system in the morning?

Hello I've had a Jura F9 Piano Black for a few years now.
It's normal in the morning for the F9 to rinse after it's switched on. If I choose espresso, for example, it's made and that's it. This morning, however, the system seems to have been empty because no espresso was made. I was asked to turn the hot water knob and then hot water ran out from under the hot water spout and the display said System is filling. Why was the system empty? Did I drink too much yesterday? Something like this happened to me years ago shortly after I changed the Claris filter, so I thought that I might have inserted the filter "slightly incorrectly". And now I just changed the filter about 1/2 week ago and everything has been running normally every morning and day since then, except this morning. Is it like PCs, where the system simply "goes crazy" from time to time? but soon afterwards everything is ok. Or did I make and drink too much coffee yesterday and last night?
Many, many thanks!!
Blacky