Interpolation doing Strange behaviour

I have a strange problem using interpolation. Here it goes:
4 master font, to generate instances in weight & width.
1st master data: Light Condensed > weight/width: 53/20
2nd master: Light > w/w: 57/100
3rd master: Bold > w/w: 208/200
4th master: Bold Condensed > w/w: 198/20

The masters are fully compatible. I have exported the UFO’s to Superpolator and they work just fine. Not a single coordenate of the SP graph would result in deformed instances. However when I am in glyphs & I try to generate let’s say a semibold instance with values 130/70 the instance is completely madness. The progression is more or less up to 100 units in the weight value fonts looks ok, from a 100 to a 170, the instances are completely mutant, then after that up to 208 is ok. The width master works just fine.

what is it???

Ok, right after I pressed the post button I had the strange idea that maybe the order of the masters in the masters tab could affect the result and bingo. It is actually important but I m not sure what is the logic

Can you send us the font to support at this domain? Please allow a few days, I’ll have a look on the weekend.