I am using the build 2136 but this issue seems to be present for many builds.
After working in an aspx page for a while. the bookmarks seem to 'forget' their correct locations or get messed up. If I hit ctrl-3 for bookmark #3, the page jumps to some location which has no bookmark icons. #3 is actually somewhere else and I have to set bookmark #3 again. In other occasions it jumps somewhere close to the right bookmark but not quite right. I have to manual go to te correct line.
I am not sure but I think the bookmarks sometimes are not keeping up with the edits.