child records not displaying on form

Are you pointing to a specific report to use on the form Properties?  My guess is that the report you are using inadvertently has a filter.  

This is most likely the same bug I ran into.  Three possible problems; one is the setting you have in the App controlling how the embedded reports display - you may need to turn on the application-setting to load all embedded reports when the form loads.  Second problem might be if you have a connected application to a parent-set of records.  I found that application permissions on the Cross App were being ignored and data was not made visible in embedded reports - so I had to give my user access to the parent-application with a very-locked-down role.  Lastly; Mark's comment about filters in a report could also be the problem.  The first two are ones I experienced from the previous rollout (not the one from Sunday) and as far as I know those bugs have not been resolved yet.