Webservice 500 error

[Amazzing]

I am using webservice  to get informations about different resources from a shop. 

Most of resources work fine. 

But 'combinations' and 'guests' return error 500.

HTTP/1.1 500 Internal Server Error
Server: nginx
Date: Tue, 16 Sep 2014 21:22:12 GMT
Content-Type: text/html; charset=utf-8
Content-Length: 0
Connection: keep-alive
X-Powered-By: PHP/5.3.27 

Most probably this is related to big quantities of these resources.

If I access shop directly, all combinations work fine. 

 

So, it looks like there is a limit of resources, that can be transferred through Webservice. Is it possible to change that limit somehow?