Hair offset when view is rotated Hair was fine, pivot was fine ... changed view from front to side ... notice how all child objects move on other pivots

some times the rigging jumps out the mesh and becomes all twisted
Sorry it took so long to get this back
I'm not sure if I can help. On my iMac behaviour is much weird than on your.

But definitely is incorrect dimensions you operate with - Location of your object in your file is
X = 119 Y = 448 Z = -28 (miles)
Clear Location Alt+G brings object to zero coordinates, it fixed glitching.

Than I wanted Apply Scale Ctrl+A that is always recommended, but it doesn't worked as supposed to. It brings scale to one as, but Dimension jumped back to original object scale (5 miles).
I had to use Apply Scale Deltas.
So try those steps if they help in your case as well.
From your View &gt; Clip &gt; End 1893939412 miles I see you fight with scale/dimension. In general - it is always better to Apply Scale. Also you have set in Scene Properties &gt; Units &gt; 0.0254 that is something I don't know what represent (since 1 km = 0.62137119224 mi), but I never used this feature.
After all this, when I tried add Hair Children worked fine.

BTW opening your file in 2.9x is even crazier disco :)