Intermittent start

Hey, I drive a gu patrol y61 lpg and gas 4.5 has had. An issue where over a couple of months wouldn’t start sometimes just continue to crank then eventually start and go fine for a good couple of weeks then do it again now it won’t start at all nearly all the time and been at mechanics for the last three weeks
Changed
Coil
Spark plugs
Fuel pump
Cleaned tank
Checked all grounds In engine bay
NATS light does as it should
Flash when no key is in ignition
Off when key is inserted

Mechanic said he traced it to ignition area and when you tapped it it would start 99% of them time told me to come get so I could take it to auto sparky
Not it won’t start at all no matter what I touch

Any ideas

Did he check or test the ignition switch/key? Perhaps the barrel contacts are worm?

If contacts are worn would car still turn over
Meaning would it still crank

Yes it may still turn over provided power is getting to the starter solenoid. What I am focused on is your comment around 'tapping it' which I take is around the ignition area or barrel. If the contacts are worn it may depend exactly where the key contacts are touching to make the electrical path to the solenoid. Is the engine turning over, as its unclear from your description. If it isn't turning over I would look at the barrel, check the voltage or condition of the battery, clean battery terminal, you have checked earths so that is out. Have you had the vehicle in water, ie is there a chance the starter is full of mud? Fusible link could be another area to look for corrosion. Do you have a fuses or fuses for 'engine control' in your fuse box = check they are not blown and are correctly seated and tight in their holder = this happened to me on trip.