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The regen issue you mention may be a point of interest...the fans always kick in when a burn is in progress and in my old bus, with the use it gets, if a decent burn isnt achieved the fan will scream....had that happen after a self induced overfill at oil change....elephant nose had around 3mm of oil sitting at the low point....fitted a catch can...thanks again to Jeeper6....filled to correct level and only time it screams now is after 4-5 burns have been initiated but not completed....in mine....its a sign of a burn in progress..if your dpf is blocked/semi blocked....the fans are a symptom....workshops mentioned on this forum could assist with an 'over the phone' diagnosis....your location isnt mentioned so hard to recommend which workshop to contact/take the vehicle to for a full assessment....Ormeau Qld, Coffs Harbour and Hornsby NSW and Springvale in VIC are the guru workshop locations.
Good luck.

ps: the 'funky' smell from the pipes is definitely a sign that a burn is in progress