Vauxhall Vectra C 2007 1.8 Design Estate - Vectra C Electric Tailgate - leestudd

Have an issue with the electric boot as in it will only close halfway, then reopen. Quite common problem when I googled it and looking at the history of my vehicle its been worked on before. I'm just querying the obvious fault/solution. A new motor is apparently hundreds from vauxhall. I've seen threads suggesting that the potentiometer being replaced would fix it, some threads saying you can get away with cleaning the locking mechanism and struts with electrical contact spray and WD40.