Firstly, reduce your retraction to 2 mm at max (for me 1 mm and 1.5 mm worked best with the Micro Swiss).
Secondly, and more importantly, be sure that you have a good thermal connection between the aluminium tube and the cold end block. And the same counts for the cooling fins and the cold end block. Use thermal paste (they should have included that in your package) to ensure a good thermal conduction from the aluminium tube to the cold end block and the cooling fins. If you have a bad thermal connection, there will be a larger volume, in which your filament will be "gummy" - which increases the risk of blockages.
(Fun fact: I had the described issue(s) before changing to Micro Swiss and never had any issue afterwards)