When I use Shift + right-click to rotate a model in Composer, several things happen:

• The regular crosshair cursor becomes a "Rotate Mode" symbol that won't go away.
• Zoom on the mouse wheel stops working.
• The rollover highlight function stops working.
• When using the Translation gizmo to move an item, there is no white arrow, and no move preview.
• There is no selection envelope until I release the mouse button.

I'm using Composer 2019. I've tried repairing, and then reinstalling the program. So far, no luck.

Any suggestions for why this is happening?