Reproducing Steps:

1. start zssapp, open a blank sheet
2. type "abc" in A1
3. right click directly on A1
4. set A1 to bold style with context menu

Actual:
A1 remains normal font.

Expected:
A1 becomes bold style.

Detail:

The key is when right clicking an non-focused cell, context menu doesn't work.
First click always doesn't work, you must select the same cell and do it once. The second click can work as expected, because 2nd time the cell have gotten focus.

But if you expand the font size drop-down box first, choose an item, it works correctly for the first time. I notice that when expanding the font size drop-down box, the selected cell gets the focus.