Frozen cold water pipes

[Happycamper2020]

Have a 3671Fl Montana. Furnace on, water in fresh water tank. Cabinets open, two mornings in a row cold water in the island kitchen sink, and water to the toilet next to kitchen water froze. No other water in faucets including upstairs toilet have a problem. We noticed living room up stairs has a strong flow of hot air but kitchen and bedroom low flow. Not sure if that's the reason for those pipes in the middle of the trailer freezing or not getting warm air in the underbelly in that area. Where should we start to look for the problem? Underbelly does get warm air we have liquids next to a door and does not freeze.

[MandK]

Is there a possibility that a duct hose came loose and fell off an outlet? We had that problem a few weeks ago in our bathroom. Noticed the heat was not coming out of the floor duct. I removed the floor outlet and saw the flexible duct hose laying in the belly.
Mine was an easy fix. I was able to reach it through the hole with a pair of grill tongs and reattach. You might have to remove some basement walls to inspect.

[Rondo]

If you remove some of the basement walls also check to see if the vent coming from the furnace and going into the underbelly has come out of its position and sitting on top of the basement floor. This happened to ours and all I did was push it back down into the underbelly and now have heated air from the furnace going into the underbelly. You can also check to see if the vent going from the furnace to the main duct running down the center of your unit where the registers are in the floor may have come loose from its connection.

[Daryles]

Under your Kitchen island you will see a panel in the corner. Take it off and you will find a hole that goes all the way to the underbelly. You could put a small fan or hair dryer on low blowing air down there to keep things warm below. You may have something similar under the bathroom sink.
I'm sure the toilet pipe branches off the bathroom cold pipe.