Windows Terminal version

Commit 6ffc3dc

Windows build number

10.0.19041.1415

Other Software

No response

Steps to reproduce

1. Enable the experimental passthroughMode opton.
2. Open a WSL bash shell (although I think all shells are similarly affected).
3. Start typing.

Expected Behavior

Something reasonably normal.

Actual Behavior

After every keypress the cursor position jumps forward several characters.

I thought at first that this was because passthrough mode was still a work in progress, since the first time I got to test it it was already broken, but I've since gone back to the revision where it was first added, and it was working fine at that point. It looks to me like I broke it in PR #12703, although I'm not yet sure how.