Those particular brakes were the subject of a recall around 25 years (1/4 century) ago. There is a gray plastic sleeve that contains the return spring. Those sleeves would commonly (virtually every single one) crack and cause that brake pad to drag.
If it was my bike, I'd throw those damm things away and replace them with an inexpensive Shamano brand V-brakeset. To do it right, you'll also need to replace the brake levers. Once you do that and see how easy it is, you'll never look back.
Also, it's easy to tell a bike mechanic who is also a liar. If (he/she) says adjusting those particular brakes is easy to do, (he/she) is a liar.
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My greatest fear is all of my kids standing around my coffin and talking about "how sensible" dad was.