Tesla shares fell on Thursday after Needham & Co downgraded the stock to sell from hold, citing a possible pick-up in Model 3 cancellations.

"Based on our checks, refunds are outpacing deposits as cancellations accelerate," wrote analyst Rajvindra Gill in the note Thursday. "The reasons are varied: extended wait times, the expiration of the $7,500 credit, and unavailability of the $35k base model."

"In August '17, TSLA cited a refund rate of 12%. Almost a year later, we believe it has doubled and outpaced deposits. Model 3 wait times are currently 4-12 months and with base model not available until mid-2019, consumers could wait until 2020," Gill added.