not one that would deter my decision continue on. In the past, there would have been a column or support in the middle of that 16foot span to carry that load.
If the steel support is still level, I do not know what caused this, but if it is slightly off center, then the beam settled and the mortar will not. I would be concerned if the beam is strong enough to support this load.
If you are concerned and you should be, I would take the pictures now, do the legal wrangling now and document the case now with the builder. Later on, they will not assist you.