So sorry that you have had any issues. Do you think the heater couldn't keep up or shut off too early, or the house is not insulated well enough?
And what froze? Interior went below freezing, waste tanks froze, water system froze...etc?
Our last RV (a TT) had that mfgt's "4 Season" option which kept us cool in the summer and warm in winter with outside temps down to the teen's with no problem.
Of course, the owner has to follow some rules when temps dip...like disconnect city water or use a heated hose, secure waste tank dump lines, secure all bin doors, install roof vent insulators/plugs, minimize main door openings, block underbody voids against high winds...etc.
Hope you find resolution and safe travels