BMW N43 Engine oil pressure

Hi all, about 5 months ago I received an engine oil pressure do not drive message so decided to take car to a bmw specialist. He told me about the timing chain issues on these engines so we decided to replace it along with the oil pressure control valve too. Now the light has come back on again. Weirdly it only came on after driving on the motorway for 30 mins and once I’ve stopped the car at my destination for 5 mins it appears when I turn the car back on. When I turn car off and on again the message disappears! Spoke to the bmw specialist again and he seems a bit confused as I am. Any ideas what this could be ?
Thanks