Take it to Henshall Engineering in Cheshire and leave it with James for a few days.
He'll sort it.
That's my best advice  Gone to a good home: 2011 4.4 TDV8 Vogue SE Buckingham Blue with Ivory and clear glass = "Rory"
2025MY Defender D350 90 in Silcon Silver on coils
1974 Series 3 Lightweight = "Millie"
Many, many other Landies over the years
My preferred specialist: www.glenrands.co.uk
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I tried them there is 2 month wait

Did some logging and exhaust sensor looks faulty?

3 EGT sensors should show continual values above 100deg and the 4th ( can't remember) is on the 2nd turbo which sticks at 100deg unless you boot it past 2500rpm. 2012 TDV8 Vogue (L322)

Fingers crossed I’ve found my regen fault

I think you're just doing too many short journeys to be honest.
Looks like it's working fine.
Sell it and buy an EV  Gone to a good home: 2011 4.4 TDV8 Vogue SE Buckingham Blue with Ivory and clear glass = "Rory"
2025MY Defender D350 90 in Silcon Silver on coils
1974 Series 3 Lightweight = "Millie"
Many, many other Landies over the years
My preferred specialist: www.glenrands.co.uk
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So the temp dropping from 260 to 100 for a split second is normal for example as that what it was doing yesterday