Hi Kizo!
To me, it sounds like your network is being overloaded with traffic. 10 machines is a lot to run on a 1Gb network, and I know there are people with less machines who are using a 10Gbe network, so I am thinking collisions on the network is the problem, where "keep alive" messages sent between the machines to confirm they are still there are being lost and so either the Client concludes the Server isn't there or vice versa.
This also sounds like a fit with the fact that using a larger packet size is causing the drop outs, while a smaller packet size does not. A test that might help in confirming this some is this - you mention " packet size= 100 mb// render time (stamped)=0:21:34// 4 nodes disconnected", it would be interesting to know with the 100 Mb packet size using only workstation + 2 clients, does a disconnect happen? Then workstation + 4 nodes, and so on. If the larger packet size works when there are less nodes in use, that would also suggest the network is becoming overloaded resulting in some keep lives getting lost among data collisions.
(BTW, you should have heard all this from support already)
The other possibly interesting test would be to use Team Render but with one of the native C4D render engines - I haven't looked into that to see if it has a similar control over packet size, but if it does you could try and replicate the same settings there and see if that has the same issue too.
A search for 10gbe will show threads where people are using 10 gig ethernet networks, so could be that is just a lot of machines and a lot of data that is more than the 1 gig network can manage. I haven't looked too far into the question for C4D in general, but I do see posts like this
https://www.c4dcafe.com/ipb/forums/topic/92259-team-render-woes-bandwidth-issues/ where it is suggested that a gigabit network can do about 100mbps, a figure I thought was interesting since that is the packet size where you mention things start to drop out.
We're continuing to look into this and discuss the subject of networking here, including considering whether some home grown networking solution may be better than C4D TR, but in the meantime this could just be a limitation of C4D TR.
If you can do those tests (100 mb packet size, less nodes; TR with native render engine with similar packet sizes if controllable) that could further confirm whether the network might be an issue. Let us know!