Hello Mr Sean.
I just want to add my thoughts regarding to this problem. For half a year I have been working with 2 Child Blueprints and I never had any problem. So I decided to create 4 more child blueprints to extend my work and viola, for literally NO reason, upon closing and reopening the editor, SOME child actors get their variables reset and appearently, this was VERY random.
Funny enough the visual component stuff was not reset, but the general variables like floats, strings, were all returned to default.
It was happening very random and I had literally no way of finding out why my old 2 child blueprints never reset but my newly created ones do.
Then I decided to delete Intermediate and Saved folders and appearently this fixed my problem for the time being. No child blueprints ever get their values reset. But I am still not sure if this is the true way to solve it.
Just my 2 cents.