Has anybody else had issues running the rear hydraulic brake hose from the rear? I can get it past an obstruction in the down tube and have tried almost everything I can think of or google has. Any advice would be great, it is the last part to the build and it is making me angry.
Sometimes yes
.
But after trying harder, it finds its way in general.
The hose has generally a curve, so you can use it to try to run it on the top/right/bottom/left of the chainstay and avoid the obstacle.
Did you try to run a cable( brake or shifter ) with a magnet to see if it goes through?
Or you can try with another hose from the bottom bracket to the back, just to find/force a path.
Good luck !