Originally Posted by bitpuddle

It is difficult to tell without seeing the derailleur, but it sounds like you might have inadvertently changed the cable routing around the cable pivot point, changing the leverage. I don’t know which version of 105 you have (they change from model to model), but there are typically two ways to route the cable to accommodate the different angles at which the cable comes up from the bottom bracket. If you reduce the leverage, it won’t shift up correctly.