WordPress iOS app make domain unreachable for 3 hours

Hi,

I will do my best to be as clear as possible.

I have 3 unrelated domains, currently at the same domain provider (OVH):
– 2 personal domains that I bought years ago. One has a 10M web space, the other redirects to the 1st one.
– 1 personal domain I bought a few weeks ago. It has a 1G web space. This is the one I installed WordPress on, to create a photo blog.

I installed WordPress and didn’t set up anything except database access.

I have a broadband cable internet connection accessible via wifi. I also have a 4G connection on my smartphone.
It is an iPhone and I installed the WordPress app on it.

Here’s the problem:
When I’m over my local wifi connection, on the app, when I do something related to Media (upload, refresh the list, trying to delete some), I get an error and lose access to ANY of my 3 domains (2 of which aren’t related to my blog). I also cannot access some pages from my domain provider, like forum.ovh.com.
This lasts for 3 hours, and then I have access to them again, like before.

When I do the exact same thing over my 4G connection, I have no problem at all.
When I do the exact same thing over wifi through the admin web interface of my blog (so not the app), no problem either.

I tried to look at the server-side logs but haven’t noticed anything remarkable, I’ll have a better look later though.

This makes me think that there is a problem between the app and my broadband router. Something the app sends or does, and that the router doesn’t like so it bans a whole range of IPs or an access node to these IPs, but I have not found what it is.
It seems that my router has no enabled integrated firewall.
I also tried to look the matter up on Google, but haven’t found anything yet.

Are you aware of this kind of problem? Would you have any suggestion about where or what I should look for?
I wanted to install WordPress to avoid getting too technical and just focus on publishing photos, seems like that will not happen anytime soon…

Regards