Whirlpool side by side fridge/freezer problem

I moved house 6 months ago and transported my fridge on its back.
It was like that for maybe 10-15 mins.
it has sat idle for 6 months until Wednesday when I plugged it in.
The display came on along with the motor and all the rest, but it didn't cool down.
an engineer came out, changed the drier and re-gassed it and it worked.
switched it off, lifted it into the house,plugged it in........same again.
Engineer came back , new drier and gas, switched on, it worked until 5 hours later.........same again.
He said there is nothing he can do about it as he thinks the oil from the compressor has gotten into the pipe which goes to the drier and that's what is blocking it.
It cost £800 4 years ago and I really don't want to bin it.
Any suggestions?
( apart from don't transport it on its back again. )

To start with, I would be searching for the gas leak. Oil lock in the drier would be unlikely as the compressor would generate sufficient pressure to remove it.

There is a auto test funtion on some of these but activating it is something they wont tell you, this test will check the PCB, light, defrost heater, fan, in sequence if there is a board fault which can throw up all sorts of weird issues it will stop and procede no further, compessor is usually the last test
there is one thing you can try, press and hold two of the buttons at once usually whatever two are flashing hi temp, door open, etc when the buzzer and flashing lights stop let go of the buttons, try this it may work
Dev