Frame Rate drops to 30 with Dell P2415Q 4K
According to Anker's community site  (which is unofficial, community backed) the USB-C hub only supports 4k at 30 Hz. You would then never be able to achieve 60 fps with this hardware.

I would contact Anker's customer support and get this confirmed, and see if you have any means of returning the product for a refund with the seller.