This phenomenon gives me the shivers...

Looking at my '' movie''  you may get the idea that this whole is a manipulated thing but I honestly assure you that I only have added the red arrows to the gif.  A difference of about 80 units concerns more than a simple discrepancy.

The dwg can be downloaded over here.

I do appreciate your reactions, in particular when this event does not occur in your DS.

Greetings, Gerard

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Then, thinking it over, I wondered if the cause could be a 'Z-discrepancy'. So gave it another try:

This arc's properties were as odd as the previous ones. 

A length of 99.9 units (with a Z-difference of only 1 unit)  where it shoud be 32.49 units.

And what about the enclosed angle(s) ?

What is /am I doing wrong ?