[PopUp Pro] Pop Up Pro creating session on every page causing cache misses

Hi we recently installed this plugin and it started causing 503 erros on our site. The server admin found that the plugin was starting a session on every page causing the cache to break. Here is what the admin said:
I checked, and the problem I'm seeing is that your site isn't hitting cache due to the use of PHP sessions.

This is preventing all of your pages from hitting cache and it's causing more strain on PHP which in turn is using more resources.
When curling the URL's you can see that a session is being set and the cache is being missed:

curl -sI https://www.weareteachers.com/grammar-puns-jokes/ | egrep 'Set-Cookie|X-Cache-Status'
Set-Cookie: PHPSESSID=7c83s5iupbbnpt818356tm5ci3; path=/
X-Cache-Status: MISS
After checking further, it looks like the popover plugin is the cause for these sessions being set.

It is setting the following headers:

Set-Cookie: PHPSESSID=q6qsbktjdl8ap4og773a2s8ok5; path=/
When checking through your plugins files, I noticed that these are being set in the popover plugin:

134 if ( WDEV_SEND_P3P ) {
135 $p3p_done = false;
136 foreach ( headers_list() as $header ) {
137 if ( false !== stripos( $header, 'P3P:' ) ) {
138 $p3p_done = true;
139 break;
140 }
141 }
142 if ( ! $p3p_done ) { header( 'P3P:' . WDEV_SEND_P3P ); }
143 }
145 session_start();
I suggest having your developer or the developer plugin review this plugin and see if the logic can be changed so these sessions are being started on every page, as it prevents your site from hitting cache and causes extra load on the server.