Shake and vac it!
sorry a personal joke...
Personaly this myth about wick back being created when using hwe on low profile carpets needs to be put to rest!
For instance, i demo cleaned an area of low profile carpet
5 weeks ago in a health center. I later found it it was carpet tiles (it was that minging!) these tiles where 10 years old and never been cleaned, apart from vaccing. And bear in mind that its a very busy health practise open 6 days a week! Infact, the day i did the demo, the manager choose the worse traffic lane that had stains that looked like coffee or coke on it!
Anyways, this 8m x 3m area that i cleaned came up like new! Fast forward 5 weeks +, I went round yestarday to actualy measure up and quote and that area is still clean! Even tho people where walking on it once i left!
I could go on and mention other times where i get great,
long lasting results with low profiles using nothing more than hwe but i cant be bothered lol
So riddle me that vlm'ers and lm'ers alike!?
I think its down to the person behind the wand and possibly the chems used.
So to answer your question Graham, crap technician and probably left the carpet too wet.