Lets start with who do you use for hosting. That might be a big part of the problem.
If the plugin addresses the cron too much this could be the case. i see the need of quality testing of all independent developed plugins within the Oxwall store. We at present have no clue how they are addressing the cron with cron jobs. The problem may be in your hosting or you would be using lot of 3rd party plugins which will lag the server..