I have this weird error with a MikroTik router placed after a UPC modem/router in CH (Switzerland). I think it has something to do with the IPv6 being active on the UPC device (Connect Box) and the NAT behind NAT setup in my case.
It first looked like MTU size problem, but i adjusted the MTU and MSS accordingly and unfortunately that didn't solve the problem (yet).
When browsing with a client (desktop, laptop or smartphone) behind the MikroTik i random get timeouts. Chrome on desktop/laptop showing: ERR_CONNECTION_TIMED_OUT
No matter what i do/change, once (or more) a minute i get this error. Services like HTML5 video/IPTV, SIP/VoIP or WhatsApp work like a charm.
Anyone who can point me in the right direction for debugging/solving this issue? Thanks in advance!