I have a similar but slightly more annoying issue, as the same(?) bug ends up with my note being deleted. I can of course just undo, but with the way I'm using it, I'm finding myself having to undo once per note (as you mentioned, after going back it works the next time within the same note).
1. Write first line of note
2. Press enter --> cursor remains on first line as mentioned by @drichli (continuing to type also continues on the first line, unlike for @dvasyukova, but later doesn't lead to the issue of notes being deleted; see attempt 1)
3. Press enter again to move cursor to second line
4. Press tab to indent second line --> cursor appears indented, but on 3rd line
5. Press delete --> cursor goes to beginning of 3rd line
6. Press delete again --> cursor goes to beginning of 2nd line
7. Press tab to indent second line --> first note completely deleted and replaced with a tab, leaving a blank note with two tabs in a row on line 1
Chrome Version 59.0.3071.115 on MacOS 10.12.6
Here's a screenshot that's potentially more clear.