Pagination problem

Hi

I am using this awesome plugin on a website where which I have setup using the ajax search – it is working great – but the problem is my pagination – it starts ok with 1, 2 ,3 and so on – but when I go to next page it says NaN and starts to countdown from 59, 58, 57 – I have tried to remove all my custom querys – used a TwentyFifteen theme – but nothing helps.

Is there a way to just make it show next and previous – if there is how do I do that – or does anyone know what causes this strange problem/error

https://ww.wp.xz.cn/plugins/ultimate-wp-query-search-filter/