This has happened to me several times. When attempting to enter notes, the caret simply advances by whatever the grid note value is without a note being entered. It appears to be random, I cannot see anything I am specifically doing. Three times I have had to throw away the project I am working on and start over. I am new to Dorico but there is nothing difficult about entering notes in Write mode. Has anyone seen this and what to do/fix this?
Any chance you’ve hit “,” (comma)? That’s the toggle for rest input. The solution is to hit “,” again.
That was it! I have only been working with Dorico a couple of weeks so these things happen I guess. 
Many thanks!
On a related note, what’s the purpose of rest input? How does it differ from just pressing space at to advance by the selected duration? That’s what I’ve been doing, and the comma is just an accidental keystroke that sometimes throws me off momentarily. But maybe I’m not understanding its usefulness in the workflow.
When you activate both rest input and force duration at the same time you can force Dorico to group rests differently from what the current settings in Notation Options imply. Rests that you enter like this are called explicit rests (as opposed to implicit rests that Dorico creates on its own to fill the gaps between the notes).
Ah, makes sense. Still, seems like a lesser usage. I’d think it’s rare that someone needs Force Duration for rests. I wouldn’t mind if it were a less prominent function key. But I imagine the team is hesitant to change core UI at this point (even if they agreed).
Coming from Sibelius, I was accustomed to entering rests, if that was what I wanted; here I can just spot it on the grid, enter it, and the rests fill out by default. But, as we have seen, the default is not to everyone’s liking - just look around for the debate(s) on how to implement rests in compound meter. So, there does need to be a mechanism for doing so. I do wish the keystroke for it were a little more involved - command-shift-alt-//-% - or something like that. Kidding, but it is so easy to accidentally hit the ; key that I sometimes enter rests without intending. Make it a wee bit harder, and I’ll be happy! But it does have a real use, so I can’t complain.
I remember that a fellow Dorician suggested to have a special playback sound for rest input — which could prove very useful in case of an unintended use of ; key
I also remember that Daniel found the idea worth giving it a thought, so maybe this will solve this kind of problem. In the meantime, I guess it should be possible to modify the shortcut preferences to give rests a more involving shortcut, as R Pearl suggests.