See this discussion - "Windchill and Creo over a VPN connection": https://community.ptc.com/t5/Windchill/Windchill-and-Creo-over-a-VPN-connection/td-p/655401
You are experiencing down slow downs over times when using Creo Parametric.
By elimination, you figured this is related to your VPN connexion.
In order to support our users during the pandemic when people had to work from home, the following hub article was created: https://www.ptc.com/en/support/article/cs322270
As issues can be multiple, it is a lengthy one.
Try and see for your situation.