Sluggish piano keys

[mikiwi]

I recently looked at an antique piano that was worked on by a piano technician: bridle straps replaced, looks like hammers reshaped, new keytops and bushings and a tuning. The inside looks really clean and the case is in great shape. It's a Victor by Bush and Lane. However, when I played the piano, a small selection of keys don't come back up right away so when playing those notes many times very quickly, there is a delay. I wouldn't say they stick because they do come back up, just not as springy as the rest. Is this something easy to fix or is this a sign of bigger problems down the road? Selling price is $950 (US).

[vernon]

sluggish keys on their own are generally a 5 minute job for the tuner to ease them