OutOfLine,
I see that the librxtxSerial.so in the 1.5.2 differs from the latest in github repository, maybe I messed up with git.
Now I've reverted that file back to the original found in 1.5.2, may you update your repository and retry?
(all this mess because we experimented an update to rxtx library and reverted back to the old version due to some incompatibility issues)