frequently lose access to wp-admin

I took over a site 3 years ago and it had the free ithemes security plugin enabled. From then till now I have been experiencing issues logging into my wp-admin area due to something in the plugin settings. I would occasionally get a 404 error on trying to access wp-admin and my solution was always to just disable my plugin folder using FileZilla, login, and enable it again. It only took a min to do so I never bothered trying to fix it but it has been happening multiple times a day now and makes it hard to give plugin devs access so I figured I should finally deal with it. I have tested all my plugins and I have determined it to be iThemes Security plugin. This was confirmed to me at a wp-camp where another dev told me it is a known issue with the iThemes security plugin. They said it was something to do with one of the settings that can be changed but I do not remember what one they mentioned ?? does anyone know what part of the plugin might be causing this?

Thanks!