I have the same issue. But it's not quite an issue

You can leave it like this, you will still get the coins as long as shares are submitted to the pool.
This is a bit reassuring .. although .. if the pool incorrectly displays my statistics, then it is likely that coins will be credited incorrectly (less).
Not sure, needs quite digging such problem, but someone could steal your hashrate /DNS spoofing/. It happened to the whole ethermine ~2017 year /afaik - then it was another advertised AS (autonomous system), which is totally illegal/.
Just use SSL - this might not solve your issue, but it's very good practice.
the option in config file (change by your location):
-epool ssl://us1-etc.ethermine.org:5555
@farsky - I see you using non-SSL - us1-etc.ethermine.org:4444, so I might be right.
My DNS is set in the parameters of the router, I hoped that this would protect me)
Yes, I really did not use SSL on purpose, not understanding its meaning and fearing an increase in traffic (VPN provides a channel of no more than 2 Mbps)
Now, again, the traffic of my rig stopped showing on the pool, although the rig was working and sending shares.
When I pressed "R", it was re-loggin and the rig reappeared on the pool.
Well, I'll try to use SSL, thanks a lot for the advice!
// it seems that the ssl uses only 0.2 Mbps