The daily float is too small and there are no sellers. Every day the market maker tries to drop the price to see if anyone wants to lock in gains out of fear it will drop and it fails.
The stock should keep moving up until it gets some sellers to meet the buyers needs and the float moves above 250k shares traded daily. With ISRG able to buy 1m shares this quarter if they want it may be hard for those short ISRG on the S&P to cover. My suggestion to them is get some poor option selling fool to sell some calls to them.