Two things:
When you open the vent or dump valves, do it slowly or it will splatter everything, including the lid in the capture chamber.
I prefer to recover the material in cotton candy shatter form, which is easy to remove by chilling and whisking with spatula.
To get cotton candy, leave your recovery pot out of the water bath and recover the butane at ambient temperature, though you will need to periodically dip it in the water long enough to evaporate away the ice, so as to be able to tell when the standing butane has evaporated away and it is time to turn on the high vacuum.
Remove all the standing butane with the recovery pump, turn on the high vacuum pump, and it inflates the puddle into foam, which rapidly dissipates the remaining butane due the the thin films bubble walls make.
Continue to pull high vacuum for about 10 minutes and then back fill and open the system.