Campervan engine dead at 33K

[Firefly2017]

Apologies for long sorry tale -

I bought my Devon Firefly in May 2017 (campervan conversion of a Euro6 Ford Transit Custom 290 Trend, Panther 2.0 Diesel, 130 PS) I used to get a ‘Filter Cleaning in Progress’ every 300 - 400 miles, no problem, did what it needed and then message went off. That was until 2022 when after maybe 20 to 30 seconds of the message appearing the engine would lose power and went into ‘Limp Mode’. AA called who reset the code and advised when the cleaning message appeared next drop a gear and give it more revs. Next time followed instructions but still went into limp mode, AA again same advice and reset.
Took it to a Ford garage at first opportunity who plugged it in, ‘balanced the injectors’ ?? assured me everything was ok and off I headed. Couple of hundred miles later, no message, power loss and into limp mode again. AA recommended leaving error codes on and recover to home, error codes were P1295-00 and P062D-00. Garage couldn’t look at it for a week but when mechanic checked it the codes had gone and it was running fine. As AA thought it was injectors I had the 4 replaced and it ran ok but with an occasional misfire BUT - never displayed the filter cleaning message ever since.

This year, less than 10K miles later seemed to have less power and was getting noisy when accelerating so took it to a local garage. Looked like injectors again, so 4 new ones again. No better, thought 1 or more may have been dodgy so those 4 injectors replaced.
No better, misfires, black smoke and noisy acceleration. Garage trying everything they could, checked no issues with wet belt deterioration, even brought in an engine management specialist who queried who had disabled some software functions?? Software was reset and now sometimes run ok for a short while, particularly at higher revs before starting to cough and get noisy again.

Garage did identify one cylinder losing pressure but finally advised that engine should be replaced.

I’m no mechanic but as I never got the filter cleaning message since it was at the Ford garage, did they disable this message/process that may have disguised an underlying issue?

Ford have been no help with this, so I’m wondering if others have had similar problems or experience?