Slope shows strange grid texture

Being aware that there were already similar questions concerning the output of hillshade/slope layer with an unwanted grid texture, but still I m confused, so I hope someone can explain it.
Working with ArcMap 10.7. / QGIS (Madeira), I made a SLOPE layer out of a DEM ( cell size 1×1 m) and got a slope raster with a grid texture , which I don’t want because I need to do further analyses with MAXENt.
What could be the reason for such texture and how can I eliminate it?