Hi,
to be honest, it just sounds to me like icing.
I was twice in the last month in ALA and had to fight the weather.
One of the problems is pollution in ALA. ( Smog ) These little particles in the air are ideal condensation points for FZFG for example. No or almost no wind makes it even worse.
That is for example why you got these poor visibilities in ALA so often.
The other day I was surprised myself, I took over an airplane which just came in and at my walkaround I did not see any ice. Visibility was around 1200m and temperature slightly below zero, no percepitation. I think it was about M6. Then I inspected the wing from above and was very surprised to see so much frost accumulated right where the spoilers are. You could not see it from the front or any other place then from the window inside.
We did De-Ice and left the place.
Very dangerous weather in Almaty and a unforgiving wing at the challenger jet.
Also do not forget, it was at night time, a night flight for the 2-man crew and duty times coming to a limit. There was not a lot of time for De-Icing either.
HAJ-HKG is very long, especially with a refueling stop.
Just my 2 cents...