MBP 2018 force touchpad doesn't drag

Sometimes when I drag a file using the touchpad from folder to folder the file icon bulges a bit but no attempt is made to move the file. What gives?? When it fails, I try three or four times and suddenly it works. I'm pretty sure it's not h/w because of the icon bulging and the pointer moves, just the file stays where it was! I figure there must be a new technique to this but I can't find any mention on the web.