It's NOT happening so far on my end.
Netgear 4350 with seperate VLAN for Dante and NDI. 10x Kiloview transceivers. NDI tools. Different Cams. MS Teams (NDI enabled)
Everything works as expected.

The N60 is averaging at approx 200 MB for 4K. Three signals are 600-800 mbps on the network. If things happen sporadic try to find patterns. Always when you open xyz or alway after selecting it in studio monitor for quality checks or similar things. I made a NDI bandwidth video on YT that might surprise you. (https://youtu.be/dW4eFcfTYQA) The other traffic on the network might have also influences. Monitor the packets in vMix itself. Buttom right stats menu.
The better the picture the easier to identify potential issues or bottlenecks.

Good evening. The problem with NDI dropping frames started occurring for me about a year ago on Windows 10. I suspect it happened after a certain update. After all, Microsoft has a history of breaking things that previously worked fine. My PC has an i7 10700k, so it doesn’t have e-cores. In the past, using the same 1gbps LAN switch, I could comfortably output 1x 1080p NDI while simultaneously receiving 2 NDI camera inputs without any issues. Now, even just 1 NDI output isn’t stable.

What’s strange is that if I set NDI to low bandwidth (which of course results in poor image quality), it doesn’t drop frames. So, without being able to prove it, it seems that for some reason Windows can no longer handle large streams or packets of around 100+ Mbps, like each NDI output, as it did before.

The only solution I found that works is to convert the full NDI to H264 NDI HX via NDI Bridge, and it works perfectly. However, there’s a delay of about 200-250ms, which can range from negligible to annoying. I should also mention that I see the same problem in both the NDI Studio Monitor and the OBS NDI plugin. Unfortunately, from my perspective, it seems that the only solution to fix this issue will be when, in a future Windows update, NDI crashes completely for all users or applications, so that it can be properly addressed—much like what happened with Windows 11 24H2, where vMix versions up to 26.0.0.45 would crash with audio sources.

Otherwise, since the problem might not be reproducible on another PC, a solution won’t be found. For example, with the e-cores issue, the vMix team had mentioned in a vMix live fun time show that they received reports about it, but couldn’t confirm it.

I allready did this but not seem to help too much. Also other than this i see that is impossible to 1gbps lan to have running full ndi streams and same time need to play or copy-transfer files from montage pc to vmix pc without ndi lag. I assume that the best solution is 10gbps network or 2nd 1gbps network for NDI isolated from the main "copy" lan but not possible in this stage to our small tv station.

Thanks for the info.
The switch is a simple 1gbps ethernet switch un-managed. The ndi signal is affected because in the lan card in the pc when the ndi runs it needs for example 120-140mbps receive bandwidth. Then if i copy from pc montage to pc vmix the lan card in the pc,is setup to work at 1gbps so the system sees 1gbps lan card and tries to reach all this bandwidth for copy the files. I see to the task manager-->ethernet 950+ receive bandwidth when copy (which in general is good because when i copy files i need the maximum for speed) so ndi starts lag. After file copy stops, ndi work ok again
I tried in sw stage in pc with a program called softperfect bandwidth manager to make a rule that when ndi port is active,then reduce copy file speed in order ndi to have the space to run ok, but i cant find how to setup the rule

Another thing you can try is to change the flow control of your NIC.