Quote History Quoted:
OK I'm going to be more blunt.
DO NOT PUT TWO WIRES AROUND A SCREW TERMINAL!!! Undo the original (big green wire nut) and add your new ground into it.
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Screws are designed for a single wire.
There are some devices that use clamping plates that can take two wires.
They almost always must be the same size.
If you really want to get two leads off a screw wrap a length of wire around the screw
and then use the two ends to make connections.
If you are working with insulated wire you cut a window in the insulation to make the connection.
While jumpers and pigtails do not count in box fill, being able to make compact connections
while staying within box fill rules (and practical considerations) can take some tricks.
GFCI devices take up a lot of box space, but still only count as two wire allowances.
At least that is decent workmanship.
With everything going on in that box, look for some WAGO connectors.