A fix has been implemented and should be available in the web app version v8738. If you're experiencing this issue, please log out and back in again on the desktop/web app.
This issue specifically caused tasks that were reordered on the mobile app and then modified to not sync correctly to the web app. No data was lost; however, if you edited the same task that wasn't syncing on your desktop/web app, the changes made on the mobile device will have taken precedence.
Sorry again for the inconvenience caused!