This will not cause problems, it is possible that the compiler "inserts" more elements into the release assembly and creates larger code. It all depends on the code itself.
Do not worry about anything.
EDIT: If you are really worried and not worried about speed, you can enable optimization for size. Or turn off auto-paste and see what difference you get.
EDIT: For more details, you can use dumpbin /headers to find out where the dll gets bigger.
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