WHMCS Add on for server uptime monitoring

we have purchased and adapted a monitoring system in PHP running off WHMCS. we have 4 check servers which are located in different DC's to allow for secondary checks. Problem is, we are getting a lot of false positives, and i think (believe) this is down to the way the checks work, in that, when a fail is detected, the second check is triggered from the same server, which then means, if the issue is caused by a local DNS issue on that check server, then, it fails a second time and triggers an alert, when in fact, the site is not down. see statuscake as an example of what we need to be doing so, the successful applicant will have a good working knowledge of WHMCS, PHP and more importantly understand how uptime checking works for websites, not server monitoring. please be clear on this point. please respond with some examples in this field and include web9 in the first paragraph of your pitch, if you would like a response