Is "dm_grain_test_halloweenie_sksyssss_sheindasdws_mationssadwadw" the actual full name of your map file? Because I think the issue is that string of text ("maps/dm_grain_test_halloweenie_sksyssss_sheindasdws_mationssadwadw/KOTH_VIADUCT_EVENT/BLENDGRASSTOCOBBLE_VIADUCT001_NOSPRITES_wvt_patch") is too long for Source to handle (7 characters too long to be precise), and I think shortening your map name will help.