Please ensure your servers are fully patched and the NIC drivers are updated to the latest.
Did you select Protected Network in VM Setting? Expend Network adapter then select Advance feature, here we will see Protected Network option. It is used to monitor the network connection in this adapter, if this virtual network adapter lose network connection, then, the VM belongs to cluster will failover to other node in the cluster.
Do you mean this issue happens after you disabled the NIC interface?
Please check if there is any related error ID in event viewer.
If you try to disable or unplug again, will the same issue happen?
If you want to simulate network failure, you can check the following thread for further information:
Windows 2012 R2 Cluster - network adapter failure
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