There are a few steps you could take.
- stop/start your PowerShell/PowerCLI session
- logoff/logon on the station where you run the script
- reboot the station where you run the script
- does it happen with all VMs in that cluster? If not, and if possible, restart that VM.
- vMotion the VM to another node
- svMotion the VM to other storage
- uninstall/install PowerCLI
- restart the VCSA
Since it concerns PowerCLI 6.5R1, it is installed with an MSI/EXE.
There can have been impact from patches (especially the ones in the .NET realm).
Again, a PowerCLI installation with Install-Module is to preferred.