Problem with phase changes viscosity layering


I am currently using version 2.5.0 of ASPECT and am trying to include several phase transitions in a test model. In my test model I use only one compositional field and several phase transitions. I use the tests/latent_heat_viscosity.prm file for testing.
This model works ok, I can see the viscosity layering correctly in Paraview:
set Viscosity = 1e20

set Phase transition depths = all:400000|600000|800000|1000000

set Viscosity prefactors = 1, 5, 10, 100, 1000
but this one does not display correctly the viscosity layering (for the same transition depths as above):
set Viscosity prefactors = 1, 5, 0.1, 100, 1000
In this model, the viscosities of the last two layers get switched, the 100x1e20 is like 5e22, and the lowermost layer instead of 1000x1e20 is 1e22.

I am not sure if I do something that is not ok or not.
Please advice.