I have observed the printer, and it is lifting to 6mm at 50mmpm and then from 6mm to 20mm at 300mmpm for bottom layers, i.e. it is performing exactly as per the settings.
If I decode the .ctb to a zip file and check the run.gcode file, I find the following:
I opened an issue when running 1.2.5 as follows:
Apparently this was fixed in 1.2.6
I am now running 1.2.10 and am seeing the same problem again