Disco 3 (LR3) not shifting from 4 to 3

We had a Disco 3 in for engine overhaul.
(Turned out to be an engine overhaul and turbo repair, post will follow)
Now today we wanted to test everything after the turbo was back in ...
... But the gearbox is playing up
P0783-23 (27) 3-4 shift - General signal failure - signal stays low
They had changed oil and filter and both were pretty vile.
The level is right and triple checked @40ºc
Things are perfect when the ECU decides to shift up, but downshifting produces the error in 50% of the cases.
In manual mode the results are better and I can see a longer shift signal which puzzles me.
In D the ECU sends a very short impulse and the shift regularly doesn't happen, it puts Fudge on the display and it won't shift down unless I clear the error or turn the engine off.
[GALLERY=] [/GALLERY]

Here you can see 4 short spikes in the signal of nº4 Solenoid

In manual mode the signal stays longer which most of the time means a successful shift.

What can we do? Any ideas? Apart from this problem the tdv6 goes really well now and the client wants his car yesterday.
Many thanks in advance

Hi

I have read that a dirty fuel filter can cause the F to show up causing limp mode

Easy to check via the low pressure shrieder at the back of the engine

what ATF oil was used plse

is that the only code that’s showing up

also what year is it plse and have the EGRs been blanked

hope that may help

ps, also seen the code can be, Internal lead free statorbush wear causing loss of pressure on E clutch

Also a link ref E clutch

https://www.disco3.co.uk/forum/topic108824.html?highlight=stator+bush