After investigating the attached repro project we have concluded that Unity is actually working as designed in this case. The user must update their scene to fix this, as discussed below.

Three separate issues are causing problems in this scene.

1) Surface And Probe Grid Alignment
Probes are spawned exactly at the floor surface. Due to floating point precision errors, this means that some probe rays will be below the floor and some will be above resulting in meaningless probe data (is the probe above or below the floor??). This can be fixed by moving the entire scene (or just the floor) a tiny amount up or down, so that it no longer aligns perfectly with the probe grid. This problem is not trivial to fix on our side and currently it is seen as a known and accepted limitation of APV.
2) Point Light Close To Geometry
The ceiling lights in the scene use Point Lights. Due how Point Lights are mathematically formulated, contributions from a point light can go to infinite as the distance between a point light and a surface goes to zero. In other words, point lights should not be placed very close to geometry yet this seems to be the case in this scene (the point lights are very close to the light "geometry"). In this scene you can mitigate this problem in various ways: a) Move the point light a bit farther away from any geometry. b) Use spot lights that points down with a very broad cone instead of point lights. c) Use Area Lights instead of point or spot lights. Note that (c) will require that you set the light to be fully baked but perhaps this is OK if the lights are not expected to move.

3) Low Sample Count
In the provided repro project, the number of samples used to calculate the Adaptive Probe Volumes was relatively low (for a scene like this). In the Lighting Window you can increase Indirect Sample Count and/or Light Probe Sample Multiplier. This will increase bake time but perhaps that is OK for a small scene like this.