SKM53 ignores setting speed threshold

Hello

I have problem disabling speed threshold on SKM53.

After sending $PMTK397,023 to SKM53 it returns $PMTK001,397,33D (accepting the command), but afterwards if I query for it with $PMTK44735 it returns $PMTK527,1.0001 (old value). Is it a bug of the device? Version of the firmware is AXN_2.31_3339_13111900,0412,M412_20131202.

Any advice how to disable speed threshold?

Thanks in advance.