MediumRoastSteam Which grinder have you? Also, are you catering for scale drift? If you leave it on for a while tared, sometimes it will drift up and down a bit.
So, before you do and replace your scale (mine is about 10 years old, and costs approx. £4.50).
Turn your scale off;
Tare the container;
Put the coffee in ( say 18g)
Note the weight of the container;
Grind into the container;
Weigh the container with the ground coffee in;
Subtract the weight from the container.
Did it increase?
I have a DF83.
My usual process is pretty much as you describe. I turn on the scale, put the cup that collects the ground coffee onto the scale, and tare it. The scale reads 0g.
Then I weigh out 18.0g of coffee beans. The scale now says 18.0g with the the beans in the cup.
Then I put the beans into the grinder, put the cup in position to collect the ground coffee, and grind away. I use the bellows until I don’t see any coffee coming out from the grinder. Also, the grinding noise has stopped by that point. So I’m pretty sure all the coffee that’s going to come out has come out.
When I put the cup with the ground coffee in it back on, the weight will often be 18.1-18.2g, sometimes a little higher. But never lower.
I’m sure that the increase is not due to retention, as I should have lost some coffee when grinding at some point. But that never happens.