actually ext2 seems to be way more buggy than ext1. besides this Motion Blend issue it crashes often when I delete takes from the scene browser. also fCurves window has the same problems as Motion Blend does - not so frequently tho.
but the worst thing I encountered - and I don´t know if it is me or a bug again, but it only happens with ext2 - when two takes are blended in Motion Blend -> Local Blending doesn´t work most times. click it or not - no difference (at blending area, rest of anim changes from bad to good) and that is a little bit concerning. it now also happens with ext1 but only with the last of 2 blendings. there is kind of a flip happening exactly where the last anim to blend starts. I really don´t know how to fix this because it allready worked, and now it doesn´t. I can´t imagine why all of a sudden a flip should occure during a slide from one standing anim into another standing anim with minimal differences.
It shouldn´t have something to do with the rig since it is a bone animation only in the Motion Blend.