It's been noted that V0.53 (and V0.52) sometimes emit the following message when creating profiles or linking:
"Warning: Gamut mapping is non-monotonic!"
This seems to only happen when creating a gamut mapping for a saturation intent. It basically means that the saturation gamut mapping is not as smooth as it could be. I'm not sure of the practical significance - the gamut boundary values change a little more abruptly than I really like, but colors with the gamut still seem to still behave reasonably, and the generally expectation for saturation mapping is that saturation is favoured over other factors (such as smoothness).
Now traditionally, Argyll's saturation intent has been smoother than many other profiling systems, and I think I will bump up the smoothness of the gamut mapping somewhat for the next release to restore the behaviour.
[ This message seems to be a consequence of the changes I made in improving the accuracy of modelling the device characteristics in RSPL.
If you are using the source, you can make the message go away, and improve the smoothness of the gamut mapping by changing smth from 2.0 to 30.0 at line 900 in gamut/gammap.c ]