hehe if only it were that simple. Unfortunately it goes beyond just the one plugin…
The technique they are using is sending a separate request with the same user session to WordPress and this is what is causing the problem – as 2x separate IPs are attempting to use the same “session”.
There is no simple method to deactivate the session lock for very specific requests from particular plugins.
An alternative you could try is extending your IP lock limit to greater than 1 and that should prevent your session being broken.
The ideal scenario is that the plugin developers wouldn’t require and use sessions to run this image processing… but since there are several plugins that all extend the original that operates like this, this is probably not likely to change.