I think I may have just ran into a situation like this yesterday. (not sure if it is the exact same issue or not)
When I re-parented the BP to a new Base_BP the components stopped rendering in the original BP.
What worked for my case was to revert (click the little yellow arrow next to each property) all the settings in the Transform section of the previous root component, now that an inherited scene root was added to the hierarchy.
Now everything renders correctly, and with the new base BP class.