The fact that you had it refurbished AND this does not always happen makes me think it’s you.
If it’s a mechanical problem it’s usually not intermitant. Also, if the people working on your sax were good they would have made sure the 2 octave keys were properly sealing as this can cause such a problem… the neck being loose, even if you have tightened the screw is not good either.

Do you have another sax to pl;ay? If so let me know what happens with that one.
If our saxophone is in perfect working mechanical condition and jumps up like that it means we are not giving it enough support to hit those notes. I see this all the time with students. Here’s what you can try:
Play the problem note over and over but slowly. When you hit it right try to keep the note going longer. As you’re holding it pay close attention to what you’re doing to make it play right. It will be your embouchure, throat, air support from your diaphragm or a combination of these. Usually it can be corrected by simply blowing extra hard with a more open throat. If you’re hitting and missing it this will slowly make you more aware of what you need to do to make it play properly and eventually you’ll train yourself to do it every time.
The G and D are 2 well-known culprits for this so I’m not surprised. Early in my studying I had a similar problem with middle G. Just couldn’t nail it 100% of the time. My teacher had me play that one note for about 30 minutes at a time. each time I played it it was my job to focus and analyse what I was doing right and wrong. I eventually figured it out as you will to.
I hope this makes sense..good luck

Johnny