"Internal limitation: too many fields" Excepion


after migration our C++/CLi dll from X86 to X64 i get as soos i want to use the dll The Error
"Internal limitation: too many fields" Excepion


the First Time wit FileLoadException the with TypeLoadException

It seams that the CLI dll ist to big. what i do not understand ic why this happen after migration X64 i did not add an additional Code to the dll

Is ther an easier way tha to split the dll ?