Solved! Disclaimer: don’t try this at home unless you’re feeling super confident. I’m not a professional harp maker, just a harp-making enthusiast. This solution requires having the correct type/size of screw driver for your harp. Most people will want to take their harp to a repair service professional, but mine is an hour+ drive.
In case anyone has the same problem: the string was sounding as it slid into the groove on the lever’s lower fret – the lever was just *slightly* to the right of the string, causing it to *dink* as the lever engaged. To correct the issue, the lever will need to be adjusted so that the string and the groove in the lower fret line up. I just barely loosened the screws connecting the lever to the neck and pushed the lever into position before re-tightening the screws. Great care should be taken not to damage the harp string. Have a tuner on hand to make sure the lever is still only adjusting the pitch a half step. Good luck!