The exact same files at the same time? As in both programms try to access the same data at the same time? Thats not possible AFAIK as they both require write permission. Im not entirely sure if its possible for your NAS to handle this somehow but I doubt it is.
No, the machines are not using the same files. My main server has the blockchain stored on it's main HDD, and the Odroid uses the version on my NAS. The Odroid should be the only device accessing it on the NAS.
Try re-syncing the tree and recompiling. There may be a bug in the version you pulled from their git repository.
If you are trying to run two bitcoin nodes from the same data directory, you won't be able to as one node will not be able to lock onto the directory.
Otherwise, I've got nothing else.
I'll maybe try a different version later this week. The pain is that it takes ~ 12 hours to compile on the Odroid, so it's a time consuming switch.
Also, I talked about the files above, but the two machines aren't both using the blockchain on the NAS - my Windows machine has a copy stored locally on it's main drive.