Double check where the four bolts are where the whole valve assembly is connected up to the line.
I had a leak, changed the valves and still had a leak. Called mobile repair and he showed me where the bolts are the plastic had fine line cracked. :R
Real hard to see the fine line cracks but he said he sees it a lot on older RV's. All the bouncing around puts fine stress cracks around the bolts. When he took it apart the plastic around the bolt opening just came apart.
He had to cut into my line coming out and did a residential plumbing fix with a rubber collar and bracket. I was taken back by the fix but everyone confirmed that is the correct way.
Here you can see after he took the bolt out the plastic just broke off around it. Again you have to look hard at it to see the cracks. And those find line cracks 'where' enough to make it leak.