I used byteball.fr/bb as my hub and applied the witness list change with MEJGDND55XNON7UU3ZKERJIZMMXJTVCV to replace JEDZYC2HMGDBIDQKG3XSTXUSHMCBK725. On top of that I replaced UENJPVZ7HVHM6QGVGT6MWOJGGRTUTJXQ   with bittrex address QR542JXX7VJ5UJOZDKHTJCXAYWOATID2. Then I found I was not able to post any transactions due to 2 witness changes. Why the nodes are not able to find an earlier unit posted by MEJGDND55XNON7UU3ZKERJIZMMXJTVCV and see that my transaction is actually compatible with that one?