Continuous input notes

After a few hours of work, I clicked on the note of an arpeggiated guitar chord, and from that moment every note of any instrument I click practically goes crazy; it sounds as if someone is playing a double kick drum pedal on the PC keys. In fact, the moment I switch to writing mode, the score fills with a barrage of notes one after the other. I tried both closing the program and restarting the PC, but now I can only play any score. Apart from this, whatever I do I am unable to do anything now