It's strange that the symptoms fluctuate. I don't think that this kind of situation is common and thus it feels like system specific (hardware or software).

As for my own experiences, there are reasons why they are perhaps not directly relevant to your case:

- with later versions of VMware, I'm using Player and not Workstation Pro. Since you mention kernel modules, I'm not altogether sure, if the situation is exactly the same with Pro and Player. Unfortunately, I'm not the right person to comment on possible problems with kernel modules.
- lately, I'm using Kubuntu. While the basis is perhaps the same as with Ubuntu, I think the management tools are different. Furthermore, default settings may be different

- I have also used Ubuntu Studio, which does have a different version of the kernel (low latency). I don't use (plain) Ubuntu these days.

As for networking settings, one thing came to my mind:
- network interrupts can happen, but if they are very short, you might not notice them. However, if you have Automatic Connection ON for several networks and IF it immediately tries to switch to another network, which is bound to fail, you may experience a problem. Never seen this happening, but I guess in theory this could be possible ... if the switching is too quick and several networks are set to automatically connect and switch. I have no direct idea, why this would be your case.

Exact Host OS version, network type and Guest OS versions, might ring a bell to somebody.