This can also sometimes happen if they use "green wood" in the construction of the Violin.

Violin Spruce and Maple tonewood after it's been cut generally needs to air dry for at least a few good years ( sometimes more ) before they should use it in the construction of a Violin. Sometimes they "kiln" dry the wood in specially designed, air tight chambers or dry rooms to speed up the process. This process, actually causes the wood to harden and "shrink" down to a point where any remaining moisture left in the wood from being recently "alive" is dried out of the fibers of the wood. This way when they use it to build a Violin, the wood is more stable, less prone to warping, harder, stiffer and also is frankly easier to carve because it's just not so spongy like when it's recently cut.

In some Chinese shops I've read this can be an issue sometimes with the lower-end Violins because of such incredibly high production demand, busy production schedules or simple mix ups. People make mistakes and sometimes QC messes up and they'll inadvertantly use wood that probably hadn't dried enough. So, what happens is when they use this green or "greener" wood and build it, (Violin) after a period of a few months or so, the tops, or backs, or ribs begin to shrink or "move" some due to the fact that the wood wasn't sufficiently dried enough initially. This causes little openings in the "hide glue" in the seams, or even open seams. In some extreme cases the Violin literally comes "undone" in spots, but usually it's just little seams or spots like what your Violin was showing. Even so, it doesn't mean necessarily that the Fiddle is bad, quite the contrary. Sometimes just a bit of glue in spots is all that's needed to close it up. Or, it can be left to dry for a long period and then return and pop the top to reglue or close the seam after the wood has finally dried and stabilized. However, during this time, your out an instrument, and, the repair won't necessarily be cheap. When it's bad is when the green wood shrinks so drastically that it splits the top or creates soundpost cracks or other structural issues that end up being more costly to repair than the instrument is really worth.

Even so, their statement about this being acceptable and normal was surprising and "unacceptable" and untrue just like Fiddlerman said. That was potentially missleading and in my opinion they did it because they didn't want to deal with the issue and eat the cost of having to have a Violin that they now "couldn't" sell returned. They should offer you an apology for that at the very least and a replacement. They screwed up period and the response was unaccpetable and poor customer service. I guarantee you if the Fiddle had been a 2K plus Violin or a more expensive instrument, their response would've been very different. Just my opinion. They just wanted to shrug it off and hoped you'd buy their false explanation. Very dissapointing....frankly I would've expected better.

However, sometimes what can also happen, and isn't the shop or luthiers fault is that if a Violin is built in an area of high humidity for example, and then get's shipped to an area that has a much lower continual humidity, the same thing can happen. Wood moves and shrinks and dries and extreme changes in temp/humidity can cause this as well. So, it's hard to say but I'd personally say it's one of these two possibilities as most likely. I mean, if they used green wood, this was def a QC issue at the very least of one that "got away" which does happen sometimes.