Proxy problem - Message from server is shorter than expected - Message ignored.

After upgrading our 2.4.7 environment to 3.0.2 two proxies are not receiving correct data from the server, therefor no data received from those proxies.

Error messages in the log (zabbix-proxy):
Message from 10.243.130.12 is shorter than expected 1859411 bytes. Message ignored.
End of get_data_from_server():FAIL
cannot obtain configuration data from server at "10.243.130.12":

From the server logs
sending configuration data to proxy "CZ_Zabbix_proxy_01" at "172.22.2.251", datalen 1859411
cannot send configuration data to proxy "CZ_Zabbix_proxy_01" at "172.22.2.251": ZBX_TCP_WRITE() timed out

Heartbeat messages are OK, from the GUI the "last seen" value is a few seconds.

There are other proxies on the local network and some remote ones via ipsec vpn which are working properly.

Before the upgrade everything was fine.