This has been happening for years and years...
Signs and game cameras achieve nothing. Signs are ignored... trust me. I worked for a local P&R for 8 years and we had signs for days and days... No one followed them. Plus they cost $. What is a game camera going to do? Might show you who is doing it but try to get P&R or anyone to care about it...
here is what you do...
At every cut through/bypass build a 8'-10' gap jump with holes (from where you dug the dirt to make said jumps) on either side of the launch. 8' gaps dont need much dirt... a few wheel barrows on the launch and lander. Dont call them jumps... call them "go around deterrents" or "barricades" and no one is the wiser...
Walkers wont go into the holes, riders will either hit the jumps or take the original line, and everyone will get rad AF!
Seriously though if you make the alt lines harder and more difficult to use than the original lines folks will choose correctly. Im talking big cedar logs rebared into the ground with quik crete. Logs have to be 3'-4' high or better. Walkers will still step over them but most riders cant bunnyhop something that high and will choose the correct line. You cant stop walkers... unless you have a crossbow or katana sword. Gotta kill the brain... its the only way!
Or just live it with it like I did when I was temporary TC out there.
If someone goes out of there way to cut down a purpose built barricade or dig up barriers rebared into the ground with quik crete they can have the go around... thats someone with serious issues and they shouldnt be provoked...