Thanks Pilou for noticing that!

Yes - the location far away from the origin is a contributing factor.

If your object has larger coordinate value it essentially steals some precision away from the fractional accuracy of calculations. I'd guess that this combined with using Flow maybe is preventing the fillet calculation from getting a precise enough result in one of its steps and that's what causes the failure.

It's probably something that could be fixed to work if I could find the particular step and loosen a tolerance value for these conditions which is probably currently too tight. But this is unfortunately easier said than done and it's easy for such a modification to have negative side effects in other cases.

But it looks like if you avoid either one of your current conditions, either have analytic planes or move the object to the origin the same fillet should succeed.

- Michael