Max amount of zones and shipping methods

I have written the plugin which is extending Lcal Pickup class shipping method with mine. And afterwards it ads about 150 shipping zones with 1 to 30 instances of my shipping method for each zone (that is the easiest way to setup pick-up offices – just give the title of address to the instance). After activation everything goes fine but stops about the miidle of the list. And WC cannot add any zone afetr that even. I plaed with php timings a lot adding execution time on the server – but the problem seems to be with ajax responce of backbone.js framework. MAy be smb tested WC2.6 with 100+ zones adding programmaticaly at once?