WHY HAVE 2 BRAND NEW AARROW STRATFORD TF90 MULTI FUEL BOILER BUCKLED?

I bought an AARROW STRATFORD T90 80,000btu got company to fit and after only 6 weeks it buckled all round the opening and its running out of control, then purchased another one and used different company and the same thing has happened. What are these plumbers doing wrong. Should the pumps on these be set at 1 or 3. Why are the radiators not going really hot, what is causing multi fuel fire to buckle or over heat. yesterday turned on the old potterton gas boiler 41kw. and many of the radiators are heating only slightly warm at the top and cold at the bottom,but plumbing company when they installed the multi fuel put fernox in the tank then drained after 2 weeks. i am a woman on my own and both companies after taking my money wont come back as they havent a clue what is wrong and also know that now the second one has buckled and a lot of air is drawing in from the sides its running out off control at 0. and now i need to buy another one,which will be the 3rd one. why is the heat not getting to the heaters? why has it buckled? theirs plenty of hot water. But 4 pipestats have gone on the bung, I think frazzeled with the heat and the hot water came out the tank in the loft and my ceilings came down 3 times. If the radiators may be full of rust or sludge would that stop the heat from going to the radiators and the heat is going back the way and buckling the fire. The house is covered all over with ash even in the wardropes. Worried sick and frozen with no heating. please can anyone help as these crooks have taken my money 3 times and Im left with a buckled fire and was taken to hospital 3 weeks ago with carbon monoxide poisening. Or could it be the pump is not powerful enough,plumber put a cheap one in from BQ £20. PLEASE PLEASE HELP. WHATS THE PROBLEM. Had also 29 different companies in Scotland in and nobody has a clue. England has all the specialists for these wet systems but they wont come up here. URGENT HELP NEEDED.