Connection to outside services from a pod

We have migrated our production application to OVH's kubernetes.

In general the transition went smoothly. We only have one problem with **randomly** breaking connection to "the world outside a pod".
Most of the time connection is fine, but from time to time our app, when connecting to :
- MariaDb database from your infrastructure
- error reporting system (rollbar.com)
- mail (used as part of i.e. registration process or internal notification)
we receive exception "Host is unreachable" or "Failed to open TCP connection to api.rollbar.com:443 (getaddrinfo: Name does not resolve)" or "Mysql2::Error::ConnectionError: Unknown MySQL server host 'km......-002.dbaas.ovh.net"

I.e. it happened 5660 times duting last 24 hours

!connection-issue|690x413

I would think it is a problem on our side, but it is happening only randomly for some % of traffic only.

I would appreciate your advice (customer support haven't answered anything for a few days already).

Cheers,
Maciek