SC Login popup shows an iframe of the website instead of the login form

Hello, I'm running into a strange issue with the login module.
I'm using the "modal popup" mode of the module.
Once clicked, the popup shows the login form for 1-2 seconds, and then the form disappears, and instead, the popup shows an iframe of the site's home page.
Then, when clicked again, it directly shows the home page and not the form. Only after I clear the site's cache it again shows the form for 1-2 seconds and then switch to show the home page.

Here is a link to a screen recording of the issue: drive.google.com/file/d/1pKNpoJavfrbjJvf...5ZO/view?usp=sharing
I'm also attaching screenshots of the model's configurations.

I'm using Joomla version 3.10.11, SCLogin module version 9.0.244, and version 9.0.244 of JFBConnect and all its plugins.

Please advise, how can I solve this issue?

Thank you!
 

just an add-on: the recording was made when site caching OFF (both global config and page cache plugin), but it also appeared with both of them on (global config on conservative caching).