File xxx.smx uses an invalid filetype; some sprites will not display. This is likely caused by a mod

I was watching a replay that I recorded a few days ago in Capture Age. Paused CA at a random moment and went over to the actual game in the AoE window and it was saying this in a pop-up overlay:

Got another one after ending the replay:

image

These are the only mods I have enabled (see checkboxes on left):


I don’t see any mods that would/should be causing these errors? The string of 7 mods at the top of the list are campaigns. The replay I was watching was a multiplayer random map game (2 vs 3 AI)