What brand of mount? Pics? That might help.
If you visit an RV show, you will see that there are a couple of locking mounts that are currently being used - Mor/Ryde and Moview. They look too complex to me and possibly prone to problems. (Too many parts to jam or fail).
One problem with any articulating mount is that often there is too much play in the joints. You can tighten them but you can't always adjust the excess play out. There can simply be too much tolerance between the parts. When you extend the TV out, the weight of it puts a lot of extra force on the arm and can put things out of alignment. So when you go to lock it down, parts don't line up. Double arm mounts are better in this respect.
You may even notice that you can have your TV levelled in the retracted position, but when it is fully extended, it will no longer be level. Even more so if you rotate the TV much at the same time. Can be quite annoying.
Personally, I would not use any of the locking mounts out there. Think of the damage that could happen if the mount became unlocked during transit. You really can't go wrong with a couple of Velcro straps/clips. Simple, low cost and effective. Just make sure to attach the straps before travelling.
You could always defeat the locking mechanism and add Velcro straps to what you have. By a large margin, most RVs being sold today with TVs already in them are using Velcro straps.
Gil & Deb & Dougal the Springer Spaniel