This is from Bug #1796125 “services in a snap with dependencies aren't starte...” : Bugs : snapd and should be fixed in edge and beta channels of the core snap. The way to fix it is to start all of the services one at a time in a topological sort order.
I think this is partly because of developer time not being readily available and because there’s a discussion currently going on regarding how to order snap services in a more robust and generic way. See Cross snap service ordering