I would try updating drivers, there is a new release for the T450: [link|https://pcsupport.lenovo.com/us/en/products/laptops-and-netbooks/thinkpad-t-series-laptops/thinkpad-t450/20bu/downloads/driver-list/component?name=Audio|Lenovo.com/support/T450|new_window=true]
It also sounds like a likely broken solder joint, I would inspect the joints as that would explain having to hold it at an angle.
Hope this helps :)