Small update this time to address some problems. The previous release broke on some builds of Spigot 1.15.2. In addition there was a problem with setBlockFast, which caused placement of upside-down rails to fail in Traincarts. Both have been fixed.
An important new feature is added that teleports players near their seat while they sneak, preventing them from wandering off. If there's any problems, it can be turned off in the config.yml of BKCommonLib.