Hello,
We apologize for the inconvenience.
I have checked your website on my local environment, and the issue does not occur there; everything is working as expected. This suggests that the problem may be related to a server-level configuration.
If your server has mod_security enabled, could you please disable it and then check whether the issue is resolved? In several cases, mod_security rules can block certain requests and cause similar behavior.
Please let us know the outcome, and we will be happy to assist you further if needed.
Kind regards