Stoutstien
lunk
That is a common belief is completely false. the discrepancies of thickness is the glass panels hade everythingto do with the manufacturing processes at the time. If you look at all the glass manufactured around the same time you'll find equal amounts that have thicker middles and bottoms.I remember in middle school learning about the stained glass windows in the medieval cathedrals having to get turned over because the glass flowed and the sections are thinner at the top aver the years. This caused me to place all my d20s so that the 20 was on top thinking that the plastic would flow faster than the old glass. I do not think it helped in the rolling though.
Today, I have a few sets that get put into quarantine when they are not rolling right. They need to think about what they did to my poor PC. Similar to some of my golf clubs who need a break after they caused me to hit a bad shot. Things like this cannot possibly be user error.
The urban legend of running glass originated because all the stained glass of a few very famous cathedrals were all manufactured by the same factory so they had similar flaws. the people who are in charge of installing the glass you're going to realize that the thicker part is more structurally sound on the bottom so they put it in that way.