SYMPTOM:
In a Strategy Web 10.4. Report Services Document, a grid with a fixed size, when switched to maximize, does not auto resize to fill a document panel in Presentation mode. When switched to Editable Mode, the expand icon maximizes a grid correctly.
In Presentation Mode:

In Editable Mode:

STEPS TO REPRODUCE:
Follow these steps in Strategy Web 10.4 and above.
1. In a new Report Services Document, insert a Grid in Design Mode.
2. Right mouse click the grid and click on Properties and Formatting.

3. Go to General Tab > Check 'Show Title Bar'.

4. Go to Grid Tab > Check 'Lock' under 'Headers'.

5. Click ‘Apply’ and Save Document.
6. Execute saved Document in Presentation mode.
7. Click the button to maximize the Grid.

CAUSE:
This is a known issue with Strategy Web 10.4 and above.
ACTION:
This issue is addressed and fixed in a future Strategy release tentatively planned for release in late Q2 2018.
WORKAROUND:
Switching view to Editable Mode and then back to Presentation Mode displays the grid correctly maximized
Strategy Internal Article Number: KB440300
KB440300