Q: thumping sound from rear

Charcoal canisters don’t become clogged, although in exceptional cases, they can become saturated with liquid fuel which ruins their ability to store fuel vapors. If the premature shut of the refueling nozzle is occasional that is not an issue but if occurs frequently then yes it is likely that the vent valve/solenoid and/or tubing on the canister is plugged. It is also possible that a one way flap at the tank inlet is restricted or stuck. The vent valve can be diagnosed and sometimes the blockage is readily visible. It is not unusual to find insects and dirt in the vent tube. If you would like a diagnostic on this, and part replacement as necessary, the service to request is vent valve solenoid inspection/replacement. Thumping noises, particularly if occurring while the vehicle is moving, are typically tire and/or wheel bearing related. If you request a vehicle noise diagnostic, a certified mechanic will identify the origin and cause of the noise and let you know of the required repairs.