In the “Project Launcher” setup try to disable this “Make a binary config file…” bool under the “Package” category, it looks like this:
That immediately fixed our issue with packaged builds.
…or if you don’t use the Project Launcher, try disabling this in the Project Settings:
Tbh, this is a very annoying “Fatal Error”-like bug in 5.5, we suffered a lot until find out what causing it… I hope it helps!