I'm running Workstation 15 Pro on an updated Windows 10 Pro host. I've been testing Windows 10 Pro and Ubuntu 18.04lts guest oses and have the same issue.
If I try to drag an drop, the dialog window comes up and then the VM freezes and the HOST os needs to be rebooted. I have restarted numerous services and ended / started tasks as well with no avail.
When a guest locks up, the host needs to be rebooted to get it to work again until the next lockup. The Library shows the guest vm as running but start/stop section of the specific vm is greyed out and can not be selected.
I have fully uninstalled and rebooted several times to ensure that there is nothing left over, then downloaded a clean 15.0.3/15.0.4 installer and installed it again.
I have rebuilt a fresh windows and ubuntu guest with the same results.