Many players simply don’t know what to expect when they pick up their racquet(s), so this is an example of what to reject!
This image is poor, but it gives you an idea of the lack of commitment, or understanding, or proficiency of the person that strung the racquet. If this is what they think of your racquet, reject it!
Will the knot come undone by itself? Probably not but this does not represent a quality finished product. Reject it!
The image below is the stringbed of the racquet with the “Very Bad Knots”.
Here is the problem, however! This racquet was ordered online with a “pretty nice discount” on the string so it is unlikely the customer had the opportunity to reject it!
When you receive your racquet, regardless of where it was purchased or strung, don’t hesitate to reject it if the stringing looks like this!