GMSK example

Hello. Does anyone have a working model of a simple random source or
file source GMSK modulation demodulation for comparison between the
input and output. This isn’t actually going out to RF, just connecting
the blocks in GNURadio.

source file >> gmsk mod >> gmsk demod >> sink file

The reason I ask is that I was looking at some GMSK examples in the
GRC… For some reason I cannot get the output of the demod to match
the input of the source to the modulator. The day has been long, too
long I guess.

Thank you for your time
Jeff