Operating system: Windows 7 Pro - 64-bit
Graphics card: Nvidia GeForce GTX 1060 6gb
Here is what appears to be a bug in the Mantaflow liquid calculations in Blender 2.90
In the first Blender file - manta_vol_bug.blend - the inflow object is within an effector-collision object. When the simulation runs the level of the fluid refuses to rise above the Z-axis of the inflow object. This behaviour does not happen with this file in Blender 2.83
It must also be noted that there is a severe difference of the liquid inflow rate using the same simulation numbers between version 2.83 and version 2.90. That may be a problem on its own, but I cannot say if this has any influence on the Z-axis volume bug that I am seeing.
I have uploaded two video files of the rendered results of this file.
I have also uploaded a second Blender file - mantaflow volume_bug 02.blend - where the volume flow relative to the Z-axis of the inflow object is more obvious. Strangely enough, this file when loaded into Blender 2.83 will show the same incorrect behaviour.