Cannot delete values for directives

Using ver.
On the CSP Options tab I am no longer able to delete values I had set for various directives. For example, I had set style-src and img-src (and others) to ‘self’. Now, if I erase these values and save the record, they are immediately displayed again, as if I had deleted nothing at all.
I note, too, that I cannot set the value of frame-src to anything. Once again, I type a value, like ‘self’, save, and the field comes up blank!
I am not using a caching plugin. This is not a browser issue, the same behavior occurs in both Firefox and Chrome.
Furthermore, there are all sorts of errors in the web server log, such as:
PHP Notice: Undefined index: tab in /blahblah/wp-content/plugins/http-security/include/settings.php on line 66, referer: https://mysite.com/wp-admin/
PHP Notice: has_cap was called with an argument that is <strong>deprecated</strong> since version 2.0.0! Usage of user levels is deprecated. Use capabilities instead. in /blahbalah/blog/wp-includes/functions.php on line 4045, referer: https://mysite.com/wp-admin/options-general.php?page=http-security