When running directX 11, pressing the "Alt" key to display the unit health bars etc, a glitched overlay shows up covering most of the screen when there is a large number of units. The glitch disappears if the screen is moved so less units are on the screen, and reappears if the screen is moved back over a large army.

This glitched overlay was not present in DX12 when opening this save game, and reappeared after reopening again back in DX11.

Edit: This glitch also occurs if health bars are set to always show with large numbers of units in DX11 without pressing the alt key.