I used processing.run('grass7:r.cost', params) to create a cost raster starting at one or several points along a street-raster-layer. Each cell is 1m² and the algorithm is supposed to accumulate (distance)cost up to 400m. Sometimes this works as intended, sometimes the minumum value is not (roughly) 0 as can be seen below. Is it possible that there occurrs some looping or strange behaviour in dead ends?

QGIS Version is 3.34.11 LTR. Rasters used are valid, points have been snapped to original street network. CRS and extent should be identical between all rasters.