Low oil pressure and fuel rail sensor please help

Hi can anyone please help am at a total loss, my 2013 astra elite has been saying low oil pressure to which I changed the oil sensor and oil switch, the problem still persists and my car about a month ago said service with a spanner, it went in to limp mode and took it to a garage and they reset it was fine, did the same again and it said fuel rail sensor, this got changed and the same issue happened again, the rac came out said the fuel oil pressure came up and also the fue rail sensor fault again to which I am lost as they have been changed, taken it to another garage and the only fault they can see is oil pressure as the fuel rail sensor has been cancelled, I am convinced there is an underlying issue and he said the sump will need to come off nd the seal re done, this is fair enough but why when ever it goes to limp mode, its comes up with the fuel rail sensor again I was convinced it was the ecu but she said he checked it and can see no fault, the car s on finance and had nothing but issues, even if he changes the seal am conviced it will still have the limp mode issue, can someone PLEASE HELP