Webhook for second bot on same server not possible?

I already have an official sdk bot up and running on a host, all nice and cozy. I am trying to setup a second bot to use for tests. Everything is the same with difference the port the channel access token and channel secret. But when I try to verify the webhook url it doesn't work, i get the following error at the web console (https://developers.line.biz/console/channel/...) :

An error occurred when sending the webhook

and my second bot doesn't get any events. Is there a limitation on how many bots can be run from a single ip or how can i fix this ?