@GRL No IPS/IDS enabled, firewall yes, but I did a factory reset and with default settings doing the same beaviour.

@GRL I did that as well moved to WLAN/LAN6 with a 3rd brand new cable same issue :-( Webpages are loading incomplete, downloads interrupted or not even starting. Connected an old TP-LINK 1043ND to...

@MR.S unfortunately no, the ISP is not providing the internet with RJ45 or Fibre.

@MR.S OK , I did factory reset. Then test without any specific settings. Same problem. restored config , same problem.

@MR.S Stand alone mode. Factory reset is something I wanted to avoid :- )

@MR.S I can see some interesting broadcast messages around the TCP resets/retransmissions. Not sure if this is related. 13:19:49.193496 00:14:78:00:00:ff (oui Unknown) > Broadcast, ethertype Unknown...