Cause
If vertical text isn't displaying correctly, it may be due to browser-specific behavior. At this time, this is difficult to address from Studio.Design's side.
What you can try
That said, the following methods have helped resolve the issue in some cases. Give them a try:
Set the width of the affected box using pixels (px).
Set the width of the parent box of the affected box using pixels (px).
overlapping display issue vertical orientation