Some of the issues with GV was back when the smoketech telescope first came out GV sold them without the vent holes and said they would vent
through the
threading, after a 3rd party did testing (it is on youtube) GV still said it was safe and said the person didn't know what they where doing.
Shortly after that those same pv's where pulled from the market for being unsafe.
Now that could have happened to any vendor, the reason it caused such problems was them not wanting to believe the testing.
This isn't the only issue but it was a big one, but honestly I haven't heard of anything bad since that, and the one time I ordered from them everything was fine.