some of the components are grumpier than others. Generally clicking something else and going back to the desired state works. Merge Join has typically been the one I cannot tame and have to delete/replace. We also use the Kimball component, which can get "confused".
Concur on don't use table. Part of the reason I always use a query is to use the (nolock) keyword, to limit to only fields/records of interest, but most importantly, to get sorted output.