Slash character in tags ruins metadata

If you put a slash in a tag name (not slug), you will ruin the meta-info-footer of every post, i.e. it won’t display categories anymore (for some reason).
This does not happen in default WordPress, so I think it’s specific to Polylang. Not a big deal to just use a “-” in place of slashes, but it really took me a lot to figure it out. And to fix it. Because to fix it it’s not enough to rename the tags, you actually have to delete them and remake them.