"Just in case".... Before doing that, get a really stiff toothbrush, or better a brass "toothbrush" and scrub the under side of the ejector and it's recessed seat in the cylinder.
When ejecting fired cases grit may fall between the ejector and cylinder and get trapped there.
When the gun is fired, the grit can get embedded and be hard to remove.
The grit can be so small it's impossible to see.
To help prevent this, when ejecting fired cases, hold the muzzle up so the cases and any grit or burned powder particles fall free instead of getting trapped.
If this doesn't do it, try the above trick.
Use a GUNSMITH'S screwdriver bit to unscrew the large "screw" on the right front of the frame.
Under this is a spring and plunger, remove them.
Open the cylinder and rotate it until a flute lines up with the left lower part of the frame, then slide the entire cylinder and crane assembly forward and out.
Push the ejector back and wedge a piece of metal or solvent proof plastic under the ejector to hold it open.
Soak as above for a day or so. I preferred cheap paint thinner for this because it drys.
After soaking, drain thoroughly, shake off any excess and use a hair dryer to warm the assembly to finish drying. (Note: Hair dryer, NOT torch, oven, or heat gun).
Spray in a good lubricant like CLP Breakfree and reassemble.
If THAT doesn't do it, return the gun to the Colt factory for a repair.
