The pump should draw a higher starting current for a short time when it is switched on. Together with the heating, this may be enough to cause the fuse to blow. Possibly another device was connected to this fuse circuit "after 3 months" of operation", which since then has been "the straw that broke the camel's back"?

The pump needs little power, but the heating does.
The heating also switches on only after the water tank has been inserted.

Our Lelit Bianca draws 1360W (approx. 5.9A at 230V) after switching on and is connected to a 10A fuse.
Do you perhaps have a flat that only has a 6A fuse?

I would take your Lelit Bianca to a colleague who surely has 10A (or more) fuses.

If the fuse blows there too, then unplug it and send it in.

No such malfunction for over two years! It could be the solenoid valve. Knock on it a little and see if the spitting disappears.
LG
Urs