There are BUGS inside the bubble?!
In my book that is 100% unacceptable.
New seller or not, the seller needs to make this right for you.
If it were me I would file a claim. Asking for your shipping back is more than fair.
I would demand a partial refund myself.
YOU are the buyer, and the seller needs to try to correct this wrong.
The seller may not have known, but if you can prove it, they need to correct it.
That is what makes an ebay seller a good one, the willingness to put their customer first over their profits.
If the seller still refuses, tell them that this is unacceptable and that you will go through buyer protection and leave them appropriate feedback.