Hi!
I wonder if this could relate to caching. Do you have (or have you previously) used a caching plugin, even if it is now deactivated? If so can you clear the cache and see if that helps?
If perhaps you already removed it can you reach out to the plugin author and find out how to totally remove it (as sometimes the effects of caching persist even after the caching plugin itself has been deactivated).
Of course, if that’s not the answer please just let me know and we can take things from there – thanks!