no source info when debug with "development(game)" config

if debug with “development editor”, everything is ok.
but if directly debug game with “development”, only the game module has source info, all the engine modules call couldn’t be stepped into.
i see the pdb file is correctly produced which is 100mb+
i want to know what’s the problem and how to solve it? thanks very much~

this is the debug stack, all the engine call is grey.