Don't use Loader Redux with wagons. It uses lua script to find wagons and puts items on belts through script as well.
Disable the option to connect to wagons in mod settings and use wagon > stack inserter > chest > loader > belt for much better performance.
use snapping and train handling from other mods
1.3.0 introduced a whitelist for loaders handled through Loader Redux
To register loaders with Loader Redux use the remote call
remote.call("loader-redux", "add_loader", loader-entity.name)
in on_init and on_configuration_changed