Yes, Overnight we went from a warning to a blocker with no heads up, but the warning was there all along, we all just ignored it 
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You will need to either reduce sizes externally at the source file or set up the LOD biasing.
If they are from UE market and not encrypted you can export them to PNG or TGA from the source project in UE, and resize them. Then import the resized ones into your UEFN project.
Or set up the lod bias for each texture, set Mip Gen settings to FromTextureGroup and adjust LOD Bias so the Max In-Game dimensions fall within the limits. Neither of the texture dimensions should be greater than 2048 pixels.
BEFORE
AFTER
