Need an insight into this one. Last year installed an LG Wall Mount, 7Kw Cooling only R407C

In my opinion it was never as cold as I thought it should be, I put it down to the gas. never mind.........got a call today, unit is struggling

I hooked up gauges, back pressure is settled on around 2.7 Bar..........then condenser fans cut, I hear a whooshing sound as if a solonoid has opened..........back pressure zooms up to +8 Bar..........condenser fans cut back in and back pressure starts going back to 2.75 Bar again

After a while compressor and fans stop...............after a while restart again

Any ideas anyone??