Sorry if this is a stupid question. Running Blender 3.4.1 (same issue with experimental 3.6)
Assumption: Selecting a set of vertices (more than 3) and pressing F should generally create a face. This is what I thought. (Most often it works, but not always. This is the problem.)
Case: Creating two cubes, placing them exactly on top of each other. Then dragging one cube a little along (say Y axis) to offset it. Then selecting both cubes and ctrl-J to join (I hope the picture indicates my intention.) I have now created a mesh with intersecting faces, I know. The 3D print tool informs of this.
So I attempt to manually fix this by deleting each offending face and recreate it. Thus I start by removing one face (see figure) then selecting all 5 vertices involved and pressing F. A face appears, but alas, it does not connect to all five vertices, only four (will not stick to the one pointed to by the red arrow). This is what I do not understand.
If I remove all offending faces first and then recreate them, everything works fine. It seems that I cannot do it one by one face.
(And no, I have no vertices on top of each other.)
Could anyone shed som light on why this is so? Bug of feature? (Or just me failing to understand something obvious?)