I also use it for at least 15 years. Very inexpensive and good when it is working.... I am one man lab, and always use timer, I also weigh it on the electronic scales, the bags are always have more than 90 grams by few grams. Have You switched to something else? I use 45SF alloy 45 gold 45 palladium. But I also use it for all other C&B use. Like gold crowns and custom abutments.
If you are still use UCLA what investment do you use. The problem with FugivestII when I use it for my custom abatements is micro fins and babbles close to base/platgorm of abatement, and the gold would overflow to the platform, especially if it is closer than 1mm to it. I do make sure the platform is wax free. I clean it with GC Resin monomer and alcohol. Nevertheless I still get gold on the platform. Very annoying! I use broken arm casting machine. I make sure I don't over tight it also. I blame the investment at this point.
I don't do C&B anymore. Started my own removables lab last year. But, here's what I know. Not trying to talk down to you with over detailed, just don't know what could help. We used Jensen metals. Primarily Superior, JPW, JCB, Classic IV, and Endurance in that order.
Don't know what system of rings you use, or if it matters, we used the Belle de StClair oval rings with the straight sprue bars.
We did many many screw retained and custom abutments. Very few issues aside from a rare bubble in the screw channel which would be taken care of with a fissure burr or 1/2round.
The abutment interface and screw channel would be treated with Wax-it debublizer just as the wax was prior to investing. This would be very gently blown to dryness if it couldn't be "drip dried" for time/volume issues.
When investing we'd slowly pour it so that the capillary effect would pull the investment through the screw channel and then over the interface instead of letting the investment pour over the interface into the screw channel. This is where we found the best success in preventing overcasting.
Do you use a vent? We'd put the a 20ga wire wax at the opposite side from the sprue and centered at the joint between the wax and metal. This prevented short castings, well we thought it did
I'm gonna think some more and see what else I can remember that may help you.
Edit:
We bench set for 20 minutes before going into a metal temp oven, heat soak for 1hr, then cast. We used a broken arm cast also. If we let it set overnight, we'd put it in the oven cold and rise the oven at 1800 deg c/hr to the 800c or 820c the metal asked for, then 30min heatsoak after temp was reached.