I believe this is an issue due to the new (2.1) scheduler, but these issues persist on my end despite me deactivating this feature and I am at a loss. In sum, I made a custom filter to study from that only shows 6 cards (criteria is only “tag:marked”). When I search for this in browser, I see 24 cards. I am using 2.1.40 but experienced these issues on 2.1.44 as well.
There aren’t any new restrictions. If you need to move the cards into a filtered deck, you should first ascertain why that’s currently not possible. The method I linked is a good place to start.