Radio Buttons interfere with Dropdown lists

I have built a very complicated macro-free workbook and in one reporting worksheet I have three drop down lists to select the information (ie main categories) that is displayed.  Everything worked fine with a drop down list on the Cat2 table to select more information as needed.

I then decided to tweak the sheet and added a series of radio buttons (about 20) to select from the displayed information rather than suing a second drop down list to display more details (sub-categories) from the radio button-selected category.

Since adding the radio buttons to the worksheet, the arrows on the three Category drop-down list boxes no longer display properly.  The arrow shows up when selecting the cell, but disappear when I move the mouse pointer over to the drop down arrow.  The drop down indicator reappears after randomly selecting a few radio buttons, and is actually visible in the attached screenshot.

Has anyone else come across this issue, and any ideas how to fix it.  I am using Excel in Office 365 2016 version.