There are usually a couple of reasons that your Internally Geared Hub is skipping. Please see the following recommendations to address your concerns.
1: Occasionally, when your Internally Geared Hub is skipping it means that the hub and shifter are not adjusted properly and you need to address the cable tension between the two. Below you will find a guide on how the adjust the cable tension on the Shimano Alfine hubs. Please see page 31 and page 33 for the Shimano Alfine 8 speed hubs and the Shimano Alfine 11 speed hubs respectively.
https://si.shimano.com/pdfs/dm/DM-SG0004-04-ENG.pdf
2: The Shimano Aline hubs require a slightly different style of shifting than a more traditional, outboard, chain driven transmission. For more information on how Shimano recommends that you shift their Internally Geared Hubs, please see the below manual.