It seems like we have a same problem.
We have noticed, pushing BT by 15min helps a little. But only if you do it starting with dinner and bath time. What I mean is, you have to push whole BT routine by 15min. Our little one ate 5.30pm, then bath 6.30pm and BT was 6.45-7pm. Now its 6pm, 6.30pm and BT is 7.15pm. She still wakes up around 6pm, but before moving her BT routine she was up for sure at 5am.
Hope this helps
... dealing with 5.20-5.30 EW for the last week... ughhhhh