It looks like Nikon changed the formatting of their maker note on the D7100 (actually starting with the D5200). Up until these models, Nikon used "big endian" (or Motorola) formatting and now they use "little endian" (Intel) format. For some reason the code was hardwired to use big endian rather than paying attention to the Exif wrapper. BTW the ExifTool utility also has it hardwired to big endian.
If you take the 38400 and divide by 256 (swapping bytes) then you get the desired 150.
I suspect that if you shot in Hi ISO (e.g. 12,800 or 25,600) or Lo ISO (50) then you would also be seeing a problem with PM and with ExifTool since this was also hardwired to use big endian.
I've made the change and will post a link to the fix after we do some verification. If you can send us a private message with a high ISO D7100 image that would help. This would be any ISO > 6400. We'd like a NEF + JPG pair. Also, if you could send a Lo 0.3 (80 ISO) NEF + JPG pair that would also help to verify.
Regards,
--dennis