i think his problem is heat, you need to turn you heat down because it sounds like by the third room you temp at the wand is above 200 and the siphon action wont be there at above 200 degrees.
Either your hose is collapsing (because of the heat or the suction) or your machine (the water feeding the HF) is getting too hot.
Now it could be that you're using an enzyme prespray and the little flaky things are clogging the intake of the hose inside the jug by the second or third room.
Your fix is easy regardless of the above problems. In case of the hose collapsing you just need a new hose. Here's a trick I learned to keep the hose on the nipple it attaches to. Put a ziptie on the hose and pull it quite snug before you put in on the nipple. If the hose offers no resistance going on the nipple you didn't pull the zip tie tight enough. If it won't go on then you pulled it too tight. The zip tie trick holds better than even a hose clamp and won't corrode like a hose clamp will/can.
If your machine is getting too hot then spray with the heat off. The water in most machines will get hot enough to prespray without even running the heater. With that said I should mention that I prespray everything with my heater set at 100 degrees.
If you're prespray is an enzyme and those little things that don't readily disolve are plugging your intake tube here's your solution. Mix your prespray in a bucket. Pour your mix into the jug through a strainer. I use a funnel and found a strainer that fits right over the opening to the funnel. It also helps filter out other floaties that might have gotten into your prespray i.e. leaves if you were mixing outside and the wind blows/blew gunk into your bucket.
I hopes that all helps. If any of it didn't make sense the email me for more details.
take the thing apart and clean it.sometimes they plug up.
weve all drug our fittings through the dirt or even just layed them on the groung.or how about our water supply.its impossible to keep everything clear thats why there are screens and ways to clean tips and all of that.its just part of doing business.
im thinking it has something to do with the heat.i checked the strainers and the problem is still there.it only happens about 30 min after the tm been running, the heat is at about 230 degrees.