Maximum execution time of 30 seconds exceeded

HI ,

One of our customer uploaded around 6000 contacts in the contact manager and after uploading the contacts they are unable to access inbound routes.

When try the to access inbound routes its getting "Maximum execution time of 30 seconds exceeded" error. Attached the screenshot for your reference. 

We try to increase the "max_execution_time"  on php.ini  from 30 to 60 & 90 and still same issue. If we set higher value in "max_execution_time" like 240 then the page getting displayed but it takes huge time for that.

Also if we disable contact manger then inbound routes displayed without any error.

So it seems while opening the inbound route its doing some sort of contact search and its getting execution timed out.

Is there any limit for the contact manager with contacts? or how we can overcome this error?

Let me know if you need any more info on this.