nice lamp. by chance do you know if the previous owner had it stored for a while prior to selling it? if so, perhaps it just needs to be cycled for a few days (i.e.on for 6 hours and off again for 6 hours). if you want to test different globe temperatures to see if the wax is overheating, you can put the lamp on a dimmer and slowly dim the lamp as the lamp begins to dome.
it's possible. i just like to try these relatively easy manipulations before opening up the globe.
btw - welcome to OG!
a problem with the coil is also a possibility. i would try gently swirling the globe again when it starts to flow poorly. if that and dimming the globe don't fix the problem, you may need to clean the coil. i've never done it but there are people on this site that have, and there are photos if you search for "coil."
I'd also run it with a 60 watt bulb. Does additional heat cure the problem -- i.e.: no slow, single bubble flow?
You may also want to try cycling, on higher heat. I've had a few that do that for a bit but eventually all the liquid gets worked out where it belongs (i.e. not in the wax) and then they run fine. It does take a few cycles of making hollow bubbles continuously for it to work all the way out though. Like all things lava, have patience.
Keep an eye on it, but it should be fine at the higher setting. If you can, you might try some other spots in your house first and use the existing bulb. There is a huge difference in how my lamps run depending on where they are in the house. I like to test run picky lamps in my kitchen as it's one of the warmest spots in the house (esp. when I'm cooking) and countertop height seems to work well for my lamps.
This is the same darn thing that one Grande of mine does...very frustrating. Putting a socket extension in to give it a bit more heat gets it to eventually all go to the top and then "rain" back down about 3 or 4 times then it overheats and the wax lifts off the coil and kind of just rolls at the bottom. When I dim it down at this stage then it goes back to the little bubbles. Turn heat back up...rinse and repeat. Its been cycled now at least 10 times over the past few weeks and its no better.
I'm at the point of having it gookitted...unless anyone has any other thoughts. I haven't looked at what the coil is doing when its making the little bubbles...maybe that's my issue too. I did try gently swirling/shaking the lamp yesterday while it was cold and then left it sit overnight before running it again, thinking maybe something separated during the years when it was only run maybe twice a yr...but that didn't really make much difference, if any. It still acted the same.