Jobs in folders get an invalid local identifier passed to the BrowserStack binary, resulting in this error message:

[BrowserStack] Local: Starting BrowserStack Local...
FATAL: For security reasons identifier can only have alphanumeric characthers with combination of hiphen(-), underscore(_) and dot(.). Please rename the identifier.

It looks like the buildTag which is passed to the plugin to use as part of the identifier contains a » character.