The skirt is 100% of the default print speed.
When printing at 50 mm / sec, the skirt can not fix to the bed.
Resolve by lowering the printing speed of the first layer to 50%.
However, the printing speed of the raft is 25% × 50% = 12.5%, and the printing time becomes longer.
Please make it possible to change the printing speed according to the place.
Like the image below.
