Intermittent code p0304?

Lets do a compression test for that cylinder and if okay I would swap out the fuel injector. Please use this guide to help:

https://www.2carpros.com/articles/how-to-test-engine-compression

This guide can help as well:

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Here is how to change out the fuel injector. Check out the images (below). Please let us know what happens.

Have had a compression test, 10 PSI less than others. Fault applies whether on LPG or petrol so injector not an issue. Cylinder 4 coil swapped with cylinder 3, plug 4 swapped with cylinder 1, to no effect. Will intermittent faulty cam or crank sensor cause this fault?

I would remove the spark plug so make sure it is not cracked. I also have seen defective spark plugs as well, they look new but don't work.

Plug okay, please answer re sensors.

If the fuel injector and compression is okay the crankshaft sensor may cause this issue. They don't tell us where they are on this vehicle sorry, but I did find information on what to look for. Check out the images (below).