We aware of the issue, that can cause all blocks in the BP to lose their positions on the canvas leading to random sorting.
The root cause of the issue is inadequately working save button loader delay:
If you click save button again in less than a second after previous attempt, there is a chance that underlying canvas render library will not be able to supply coordinates of all existing blocks leading to saving empty values.
The bigger BP, longer it takes to rerender all blocks during the save process.
We are working on implementing a fix for this issue. In a meantime please allow a couple of seconds between attempts to save your BPs.