I have had most these versions of the Distribute Spacing bug. Today's iteration - if I enter '.5 in' it aligns the objects 5 inches apart. It displays '.5 in' but but moves things 5 in. if I enter .05 in It aligns the objects .5 in apart.

Todays workaround is entering my value/10

It does the same thing in metric units - everything x 10

I've been having this same issue for the last several versions. Document does not have to be a print document or metric based. I work in RGB illustration documents using inches. The only requirement is for the align panel to be collapsed or hidden. The only fix I've found is to move an object while the align panel is showing, then it will update the field to show the units.

I confirm that and I had it for several versions already and even reported internally.
Thank you for logging it in publicly.
It means I am not the only one having this!

It’s quite easy to replicate it:
1. Make sure Align panel is collapse or hidden.
2. Relaunch Ai
3. Create a Print document, metric based
4. Expand Align panel
Now, if you create two objects and click one to set it as a key, the Distribute Spacing value displays no units! And if you type 1 in it, it applies 1pt instead of 1mm.
And if you type specifically '1mm' in it, Ai dings at you and doesn’t accept the value!

A workaround I know is to create a new document with the panel visible. Sometimes I am lucky to get it fixed in place, after fiddling with undo and cursing aloud.

This has been an on-going issue/bug. Sometimes saving the document updates the behavior for that 'session', sometimes just opening a previously existing document will do it as well.

It's temporary but it happens each and every time the software is started.

When ALIGN TO KEY OBJECT are selected, the spacing between different elements DOES NOT REFLECT THE UNIT OF MEASUREMENT OF THE DOCUMENT, but is set to pts (0,353 mm).

Entering a number with a specific measurement type (", in, cm, pt, px) into the Distribute Spacing field results in an error beep. The number stays, but the decimal and measurement type are removed.

When making a selection of objects and choosing a key object while the align palette is inactive, upon activating the align palette the distribute spacing value entry is grayed out.
It works fine if you make the exact same steps while the align palette is active.

The distribute spacing is set to pixels, but doesn't show any measurement. This took some trial and error to find out it was pixels. Trying to override it by typing in say "2in" only gives you an error sound and doesn't change anything.
It seems to only show the document units after playing with a few object with the panel open. I've had limited success with changing the document units to something else and then back again.

Is this related to the bug reported at https://illustrator.uservoice.com/forums/601447-illustrator-bugs/suggestions/36859432-align-units?

In that bug, the value for distribute spacing doesn't show a unit of measurement either but calculates the spacing in points.

In 24.1.3 units appear later and then stay.
Also I noticed that after initial entering the value Ai recalculates it, presumably from points into mm, resulting a different value.

Also relates to this
https://illustrator.uservoice.com/forums/601447-illustrator-bugs/suggestions/38185612-negative-alignment-value-using-key-object

Hello,

Illustrator CC 23.0.2 - after update Align (Distibute Spacing) units Key Object only works in points. I use "cm" in all document...

I think your software is falling down year by year.