Collabora "connecting" delay for 20 seconds

I’d like to invite people who want to try the libreoffice building, to follow this step (in deutch unfortunately):

I’ve builded LO using this guide on a Ubuntu Xenial VM, no 20 seconds delay, everything ok.
I tried the same thing on a debian jessie but here, no luck. I have 40 seconds delay… I don’t know why but this is a different problem… the vm performances are good (I’ve used the same VM of the ubuntu xenial) but the delay is enourmous.
Can anyone guide me through this issue? What can it be to create this long delay?

Thanks!