Mmm, e-cheque, nothing but trouble in my experience. if anyone paid me that way these days the deal would be off, in fact I didn't know they still existed to be honest. As others have said, do not let go of the bass and even if it clears - a big if - check your rights, you might find the reason the buyer has used e-cheque is to make an dodgy reclaim of the money easier.
You said above that you felt nervous, I suspect you have good reason to be honest. Hope it works out OK 👍