Have you read: Optimizing your RotoVap
Start there. once you’ve read that thread, use the links below the first post to explore further.
Do you have a controlled leak?
A cold trap?
What style vacuum pump?
What temp are you running your condenser?
Does your chiller keep up or does that temp change over the course of your recovery?
Yep. Although if you don’t have any cannabinoids in there that’s more water than ethanol. Get yourself a proofing gauge and learn how to use it.
Seems like you need to read of azeotropes/heads/tails/hearts to really wrap your head around this.