Continuity mistake: At One Eyed Jack's, when Agent Cooper and Jacques are sitting and talking there are 2 glasses of beer on the table. In one shot Jacques finishes a glass. When he gets up, both glasses are full. (00:10:20 - 00:11:40)
Continuity mistake: When Cooper is at the police station describing the events of the night of the murder, he is seen taking a doughnut and placing it on the napkin next to him. A few shots later his napkin is empty and the doughnut is back on the stack.
Continuity mistake: The position of Blackie's fingers on Audrey's chin switches depending on the angle. From behind, her fingers are straight; from the front, her fingers are scrunched up/bent.
Answer: The answer to pretty much any question beginning with "Has David Lynch ever explained _______?" is: no.