This is a Pennsylvania Civil Procedure matter. Missouri law is irrelevant.

Of course Missouri procedural law is not the governing authority for a PA court matter. Nevertheless, my experience is that procedural process in the various states often have similarities that may assist the inquirant in understanding the process of law--an understanding that allows inquirant to be better informed when considering his/her options.

You are fortunate that the responses of "a lawyer from Missouri and one from Alabama" have prompted the definitive response from atty Cliffird L. Tuttle, Jr. on the procedural issue of "default judgments" --a phrase you never mentioned in your original inquiry, but perhaps irrelevant to PA law, where distinguishing a default Jmt from one obtained after the issues have been joined may bear no relevance.

But what do I or Atty Shepard of AL know: we are, after all, "irrelevant [whose] answers should not have been given".

There is a lesson here: always trust a lawyer whose Avvo image shows him dressed in a dinosaur suit with a briefcase shaking hands with a a human in a suit... Really, how can you possibly go wrong with such 65 million year old gravitas?

The inquirer had a judgment followed quickly by a writ of execution. He says that he had paid the debt. He wants to know what to do. Although he does not say that there was a default judgment taken, chances are pretty good, given the facts stated, that this is the situation, not one in which judgment is taken "after the issues are joined." If the inquirer had filed an answer, he most likely would have defended on the grounds that the debt had been paid and the case would be going to trial. If so, the judgment can be opened, as a matter of course, under the Rules of Civil Procedure within ten days. There is more to the story, of course, but the inquirer needs to have a conversation with a Pennsylvania lawyer and needs to do it quick.
As a matter of fact, we have nothing in Pennsylvania like garnishment in advance of judgment. I'll stand by my irrelevant comment. However, I don't wish to make a personal attack on any lawyer anywhere. To the extent you took it that way, I apologize. Once this dialogue is complete, I'll post it on my blog.