Field list view "Group by" setting interferes with filtering (sometimes)

I’m trying to narrow down the case, but here is a start:

Database Node has fields ‘PreviousNode’ and ‘NextNodes’.

In the Node entity view I have a list view field that has

  • Items: Node
    Group by = PreviousNode
  • Context filter disabled.

Expected: a list of nested nodes.
Proof of expectation: In the entity view of another database (e.g. Project), I have exactly the same list view field, with the same settings. It displays a nested list of Nodes.

However, in the case described above (where the currently viewed enntiy is of the same database Node), the nested nodes do not show up.

See screenshots:
The first two screenshots show the list view ‘All Nested’ (current entity is Node) which configuration is the same as the third screenshot with the list view ‘All-Nested’ (current entity is another database).

Correctly showing when currently viewed entity is of another database: