This can happen for a couple of reasons, the two most likely ones being another map export that's overwriting the bridge meshes or your own files overwriting them, like Ruby said there.
If you haven't tried it already, completely clear out your exports folder. Just make a not about which maps you have to download again beforehand. But try downloading this map first then, and have it be the only map you have when you go to try again - if that fixes things, the issue was just another map you've downloaded, so be careful when installing future maps to not overwrite things.
What it likely is though is something else in your own mesh folders, because hey, FH has been known to make things difficult. So plan B. Go to (C:) >> Feralheart >> media >> objects. If you have anything in "my_objects", clear out that folder and restart. If you have .object or .fho files in the main objects folder that are not the default files, delete those. NOTE: Don't delete the default files in the main objects file, only the ones you put there, if any. Default, MyPlants, MyTrees, MyRocks, and Miscellaneous are the only default .fho and .object files as far as I know, but I might be wrong there.
**The easier way to go about doing this would be to obtain a vanilla copy of the objects file and swap them out, if you're unsure of what to keep and what not to keep.**
Aaaand if that doesn't work, best I can suggest to you is to search your computer for anything FH related and delete it, then reinstall the game and download the map again. Hopefully you can just wipe your exports or get a new folder for your objects file instead.