This may be it! I totally only expanded the roller as much as I could by hand...urg!In the video it sure looks like your roller assembly is fully expanded but it's hard to tell for sure. This video will show you how to expand/contract the roller assembly and replace the tube.
I would check to be sure the roller is fully expanded and the ferrules correctly installed. If trouble persists then pull the tube and inspect it for damage or even install the replacement.
If I remember correctly my pump was shipped with the roller assembly retracted.
Stenner QuickPro Pump Head Replacement Single Head Fixed Output - YouTube