We found (by Googling Internet) that last cumulative Windows 10 updates (KBs, include KB5001337) make problems with different applications.
Problem include lost scroll bar.
This is Windows update problem, not Unitronics problem.
To fix this you have to uninstall KB update and wait until Microsoft will fix this problem in additional KB update, or other accepted by Microsoft way.
Unitronics has no way to fix this.
Related KBs:
KB5001337
KB5001330
Possible other updates, dependent of Windows OS version.
B.R.