There are a few reasons why dispensary joints may canoe. Canoeing occurs when the joint doesn't burn evenly, and one side is much higher than the other. This can happen if the joint wasn't rolled tightly enough, or if it was packed too loosely. If you see your joint starting to canoe, you can try to even it out by gently blowing on the lower side.
Another reason why dispensary joints may canoe is because of the type of paper that's being used. Some papers are thinner than others, and they may not hold up as well when burning. If you're using a thin paper, it's more likely that your joint will start to canoe. You can try using a different type of paper, or packing your joint tighter, to help prevent this from happening.
Finally, if you're smoking in a windy area, that can also cause your joint to start canoeing. The wind can cause one side of the joint to burn faster than the other, leading to an uneven smoke. If you're smoking outside and there's a breeze blowing, try to shield your joint from the wind so that it doesn't start canoeing.