The bug
Hoppers are able to pick up item entities inside them, even when they have a container above (see also MCPE-80555).
However, when there are currently items flowing through the hopper from a container above, the item entities won't be picked up causing them to despawn eventually.
Reproduction steps
See
[media].
Build two hoppers above each other
Let item entities slide on ice into the lower hopper
✔ The item entities are picked upNow put items into the top hopper and repeat step 2
❌ The item entities are not picked up, the hopper prefers transferring items from above
Linked issues
duplicates 1
Attachments
Comments

Hoppers with container blocks above (such as the second hopper in the attached video) are assumed to be dedicated to that container per Prof. Mobius comment on MC-8864. This report is not describing anything different. Resolving as a duplicate.
It could be because the items are going too fast in because of the ice or the hopper cannot pick up the items because items are already going in it.