Thank you for reporting, @ottavianogr. I see the source of this issue and am working on a fix for the next release.
GH issue: https://github.com/ampproject/amp-wp/issues/5537
Hi, @cleanthinking. It appears that the BetterStudio core theme is the source of this issue, as it is calling is_amp_endpoint on the pre_get_posts hook. The best way to resolve this will be to reach out to the theme developer and let them know is_amp_endpoint should not be called after the wp hook.
