Can trains travel both directions through Bachmann turnouts or are they one way only?

Both ways.

Thanks,
I'm having issues with derailments when passing backwards through them at any rate of travel. I have purchased a Ho gauge to start checking for height issues with my track.

It could be any number of things, not just track gauge, like the ends of the switch points catching on flanges.

You might have truckmounted couplers too. We just had a long discussion about those dogs in another posting.

https://m.youtube.com/watch?v=WvfwgaOVRi4