The interesting point in the issue - the new translation is started, but the old translation attempts to load and triggers the warning  "The source page may have changed significantly".

Two improvements have been introduced since the issue was filed:

• • CX2 version handles loading (re-loading) saved translation versions in a better way generally.
• the warning functionality/visibility was changed T168287: CX2: Warning about article having changed too much

The issue might be possible - but it should be a rare case of sort of a racing condition, so if new reports come that it happens more often, then the task might be re-open