.pyc files aren't meant to be portable, they contain raw bytecode and data specific to the version of Python they were compiled on. For example, search for "Changed in version 3.6" here and you'll see all the little changes to the bytecode format: https://docs.python.org/3/library/dis.html

You'll have to compile your python source code on 3.6 if you intend to run it on a 3.6 interpreter.