SYMPTOM:
When the column headers are locked in a report in Strategy Web 10.4 and above and there is enough data for the users to scroll from left to right, when the user scrolls to the right, the data of the grid will not be aligned:

STEPS TO REPRODUCE:

CAUSE:
This is a known issue in Strategy Web 10.4 and above.
ACTION:
Currently this issue is being reviewed by our Technology team and has been scoped for an upcoming scheduled Strategy release. KB441675