Intervals appear to change position after typing and syncing

[pleath]

Describe the bug

To Reproduce

In Scriptor, the repro looks like this:

1. In client 1, type "abcdef".
2. Add an interval at {2,2}.
3. Go to offset 0 and type "abcdef".
4. Add an interval at {6,6}.
5. After syncing, client 1 correctly shows the text "abcdefabcdef" and intervals at {8,8} and {6,6}.
6. But client 2 shows intervals at {7,7} and {6,6}.

Note that the issue seems to be timing-dependent. Hitting breakpoints during typing or creating intervals hides the bug.

Expected behavior

Logs