Hi molocho,
thank you for your results. This input is very helpful.
I have to withdraw my results from last post. The issue like in your case still seems to be broken in the latest snapshot of LEDE. But still glad to hear, that the workaround does his job. 
We are currently discussing this issue in two separate threads. Since the problem of yours has been fixed for the moment, I would like you to participate, if possible, in the other thread to limit it to only one. Mt7621 DIR-860L does not support VLAN's