diesel heater issues

Hi all, hoping for some experienced eyes on this as I’m a bit stuck. I have a VW T6.1 camper (converted from new in 2020). I recently took it to a garage to have the suspension adjusted/raised for comfort. While the van was on the ramps, the garage noticed the heater exhaust routing underneath...

I had a diesel heater fitted with the conversion May 2022. We have used it a couple of times in -5 conditions, but not for very long. We went to Scotland in December with freezing temperatures but on using the heater, despite having it on for over an hour, it was only blowing warm-ish air -...