Hoppers not taking items from Chest Shops

If a chest shop has a hopper underneath it, items will not flow from the chest shop to the hopper even if the chest shop is set to Buying mode. This affects things like Paid AFK spots (since the dropper will eventually run out of sell-back items due to the chest shop not letting go of its contents), or farms that have a shulker box buy-back system for a shulker box loader like with my Maxi Crocketer. The symptoms do not appear right when a chest shop is created, nor do they go away immediately after a chest shop is removed, making it more difficult to replicate it. This is why I provided two videos: one showing intended behaviour and the other showing actual behaviour.