The only simple answer is that what you describe can't be happening, but it is. Although it seems ok, check the bypass for the water heater and be sure the bypass is closed completely. There is no reason the bypass will work differently on city water or the fresh water tank. Beyond that you may have some plumbing error by the manufacturer. Even then, getting different results in the kitchen and bathroom is a puzzler since they have the same supply unless you have one of the MHs with separate plumbing to everything, which is a nice upscale feature. Since it is new a trip to the dealer would be in order after an hour or two of effort on your part. Let us know what you find.
2014 Palazzo 33.2
Cummins 6.7 ISB, Allison 2100 6 Speed