The issue here is that you've opened a file and read its contents so the cursor is at the end of the file. By writing to the same file handle, you're essentially appending to the file.
The easiest solution would be to close the file after you've read it in, then reopen it for writing.
with open("replayScript.json", "r") as jsonFile:
data = json.load(jsonFile)
data["location"] = "NewPath"
with open("replayScript.json", "w") as jsonFile:
json.dump(data, jsonFile)
Alternatively, you can use seek() to move the cursor back to the beginning of the file then start writing, followed by a truncate() to deal with the case where the new data is smaller than the previous.
with open("replayScript.json", "r+") as jsonFile:
data = json.load(jsonFile)
data["location"] = "NewPath"
jsonFile.seek(0) # rewind
json.dump(data, jsonFile)
jsonFile.truncate()