I've determined the underlying cause of the problem - it is a blackberry issue - and I've got a workaround that works but does not fix the blackberry issue that causes it.
I was able to deduce what's happening is that the blackberry is registering 2 touches instead of 1 for some reason. The first touch opened the popup and the second touch, if the button/touchpoint was in the same pixel area as either the 'close' button or the translucent black underlay that also closes on click, would register as a click on the button/underlay and close the popup right away. That is also why it was happening intermittently, if the button to open the popup was in the area of actual popup then it wouldn't close because the second click registers in a non 'closing' area.
TL;DR: It's a blackberry issue that they need to fix.
The solution was to disable the 'click to close backdrop' via 'data-backdrop="static"' only on blackberry.
I used the following in JS:
In the section where I check for supported stuff and add classes I have this:
if(/BB10/i.test(navigator.userAgent)) {
//BB10 Device
$('html').addClass('bbten');
}
Later on just before I register the click events to activate the modals, I have this to add the static (not click to closeable) backdrop if it's BB10 (3 different modals #contact, #signin and #signup):
//bb10 double click issue
$('html.bbten #contact, html.bbten #signin, html.bbten #signup').attr('data-backdrop','static');