A.O. Smith is an excellent brand, especially for commercial units. It appears that the unit just needs to be serviced by someone that knows what they're doing.
Call A.O. Smith and complain if you didn't already.
Any new commercial unit will have "doodads", (ignition module, controls, electric flue damper, etc.) and will only carry a three year warranty. Another point, it sounds like you're operating a food service establishment. Although the dishwasher booster requires 140F to boost the water temp to 180F for the DW's final rinse, it's not a good idea to have 140F feeding restroom faucets or even sink faucets in the kitchen. A tempering valve may be needed.