Use internal speakers with others plugged into headphones jack

It sounds like a hardware problem in the jack. If you can put pressure on the external part of the plug and change it: cause static or breakup it's probably a hardware problem in the jack.

If you had said you only tried one set of headphones then I'd have said it's probably a problem in the headphone plug but if it's multiple phones and speakers then it's probably the jack.

There's a sensor in that jack that monitors if something's in it or not to switch off the internal speakers. The if there's continuous sound, just switching from internal to external the problem may be that sensor. If the sound cuts out from both internal and external once in a while it's probably the jack.

If the MacBook Pro is still under warranty I'd have Apple look at it, they'll swap motherboard to make it right if it's a hardware problem at no cost to you.

When a USB device is hot-plugged while VMware is running, I often see a dialog from the VM instance asking if the device should be attached to the VM or to the host OS. It's quite easy to miss this dialog if you have other applications running or if the VM is in a separate workspace. And until the dialog gets its answer, the device isn't attached to either OS.

If you're not seeing this dialog, it's also possible that VMware has already been configured with a default answer for the device in question. For example, it might automatically be attaching the device to the guest OS running in your VM. Note that this is not normally what you'd want with USB speakers, as VMware already emulates a virtual audio output device for use by guest OS's that funnels audio output through the host OS.

Have a look at your VM settings under "Virtual Machine > USB & Bluetooth Settings…" where you should see a dialog similar to the following:

I expect you should see an entry corresponding to your USB speakers. If so, you should be able to configure how they're handled when hot-plugged from there.