This seems to be the bug described here or something similar. It affects raster layers when the bounding box is bigger than the raster layer. When you zoom in, everythin is perfect.
This behavior is common for my QGIS installations on different machines with EPSG:4326 as project CRS (not 3857 as in your case), see screenshot with rasters in the same CRS (4326) as project:
Strange enough, setting the project CRS to 3857, leaving the rasters at 4326, it works well:
Apart from disturbing visually: is there a reason you want to change that? You need this small scale view? From my experience, this affects only visualization, not processing. So a workaround is to just ignore it. If you really need such small scale visualizations, you should reproject or change you project CRS. Fixing the bug - or funding it's fixing - would be a nice alternative: https://qgis.org/en/site/getinvolved/donations.html#