When I try your script, but add log => ['debug'] to the constructor, the script prints the following over and over:

[DEBUG] 
.------------+------------------------------------------.
| type       | content                                  |
+------------+------------------------------------------+
| command    | repl.ejs("repl.getAttr(578,\"busy\")\n"- |
|            | ,"");                                    |
|            | --end-remote-input                       |
| result     | "{"status":"ok","result":{"result":0,"t- |
|            | ype":null}}"                             |
'------------+------------------------------------------'
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