NO HEAT OUT OF REAR DUCTS on 38RL

[JSTorsrud]

I have been scratching my head as to why I am not getting any Heat from the REAR DUCTS in our 38RL.

I have checked the Flexible Duct work in the basement and Cannot see anything that has come loose!

Can the Duct Work that leads to the rear ducts Collapse?

Any thoughts on this matter will be appreciated!

Thank You,
Jeff

[Ford truck guy]

Below are pictures of the HVAC lines that run from the Plenum to the rear of the RV... As you can see, it was almost 100% blocked...The 1st 2 pictures are of the original, the last is what it now looks like... I had it rebuilt by an independent RV repair shop. Before repair, I could hold a lighter at the rear vent and it would stay, now as soon as I turn on the heat, the lighter will be blown out.