Vuescan & B&W scanning. TIFF or DNG. 16 or 48 bit

Normally I have been a keen follower of 16 bit raw DNG scans for my B&W scanning workflow on Vuescan and NLP. The benefit was much smaller file sizes and no noticeable difference in results or workflow over using 48 bit raw DNG.

I have suddenly had issues with 16 bit raw scans coming out much lighter (and therefor darker once inverted in NLP.) I do not know if this is an update issue with Vuescan as this is the only differential in my set up.

In tests, 16 bit grey TIFF Linear Scans and 48 bit raw DNG scans have been as expected. It is just 16 bit raw DNG scans that seem to have changed.

I have also put this on the Facebook page discussion forum if you want to see examples.

Any thoughts on what might be happening?