I see you have no answers, so I will have a go. Carpet shampooers in my experience are devils for getting lumps of set shampoo in the spray hoses which are very narrow bore plastic., especially in the machines that use hot (not warm) water or which have a water heater built in. A dedicated DIYer might be able to disassemble the machine and unblock the hoses but its an expensive job if you have to pay to get it done.
prevention is to use the shampoo well mixed and diluted and to use cold to luke warm water only in the machine.