Drivetrain error flagging up DPF

[GHW894]

First time poster here but long time watcher haha!

Having no end of problems with my 63 plate 116D 1 Series.

Few months ago it flagged up a drivetrain error, then begun to break down regularly and it showed my DPF was clogged but unable to auto regen. Cue many force regens to get it running.

Anyway… finally got sick of it and took it to BMW as no garage could diagnose this drivetrain error. Been with them for a little over a week and they still cannot find what is wrong with it. They keep thinking they’ve solved it, take it for a drive as the diagnostics tell it a regen is needed, it clears the drivetrain light and then a few miles later it’s back on.

The garage commented that there is a slight oil leak around the seal in the rear diff and I’m wondering if this could have anything ti do with it. The fault code coming up all goes back to the DPF but I’m just not sure it’s the actual DPF at fault, more something causing the code so the DPF isn’t able to regen.

Anyone got any ideas? It’s driving me nuts