Limit on number of checked checkboxes in discussion forum's permission management?

We are in the process of developing a new website for a client and have installed the discussion forum. At their request there around 250 member groups on the website. All appeared to be work fine except for some reason, there seems to a limit to the number of checkboxes that can be checked when trying to change member group permissions in the Forum Management.

When we check (or tick) checkboxes for each member group (under ‘Can View Forum’, ‘Can View Hidden Forum’, ‘Can View Posts’, etc…) we tried to select all the checkboxes for every group (allowing full access to all) with the exception of Guest, Pending and Members. However when we click on update to save the permission changes, the green tick appear showing it saved successfully, however only the first one hundred or so member groups actually have their checked (ticked) checkboxes. The rest have not actually been saved at all meaning no access to forum. Unchecking checkboxes that did saved successfully and then checking checkboxes further down the page works, which makes me think there may be a built in limit to the number of checkboxes that can actually be checked/saved.

I understand that there are probably more member groups than are intended for ExpressionEngine but does anyone know if there is a way that I can get around this, or perhaps a way to increase any limit if that is the cause? I’m not sure where I would go to find the code for this (Whether it’s the forum module or just ExpressionEngine in general).

Any help would be very much appreciated. Many thanks in advance!