I have not seen this on my side. What kind of network are you connecting to? A few more details about the network may help track down the solution.
I am not an expert in networking, we just have the most basic of networks, our dept has 6 Mac pros , with one designated for network rendering / storing common footage. We just connect through finder to the render Mac so nothing third party going on.
It's something different with cc vs. Cs6 and it has happened on all of our machines. Back in cs6 still works smoothly.
My thought was maybe cc checks all footage differently on every action and since we are pulling so much from the network it was slow. The main comp has maybe 40 layers, with other precomps in it.
Last resort is to format and reinstall osx and all our software but it's a guess and one that would involve a weekend of unpaid work on my part ugh.
What exact version of After Effects are you using? 12.2? 12.0?