There should be no click on the upstroke (I actually quite hate that click, since it detracts from that nice downstroke click + bottoming out harmony when typing on clicky alps). At most, there should be kind of like a subdued ping. I noticed that when disassembling switches, especially if they are not in nice condition, when assembling them back, some combinations of top housing/slider/click leaf will exhibit a click with a greater chance than other combinations. That's why I now always keep parts together when cleaning them. If it happens in the future, try rotating the parts a bit. It can be tedious, but it could help.