The reason I have had water intrusion is directly related to my choice of canvas and the unfortunate lack of a drip edge.
First mistake: I decided to use a lite 5oz waterproof canvas instead of the industry standard 16-18oz vinyl coated polyester.
Second Mistake: My initial idea for a drip edge did not work out as I had hoped. The first winter I had no drip edge at all and while the unit was closed the small edge of exposed canvas would become soaked beyond it's waterproofness and then start dripping inside the camper. I solved this issue with Duct Tape and that solution worked for about 1.5 years without fail. I could have probably replaced all of the duct tape and been just fine for another 1.5 years.
I'm sure if I really wanted to I could have come up with a better solution this summer and removed the old canvas and installed a proper drip edge. However, there are some items that my camper was missing and would always miss due to its size so that is why I decided not to pursue repairs.
I will say that after three years of heavy use. Spending roughly 9-10months sleeping in it and driving many thousands of miles off road the camper has held up and done an amazing job. I am excited for the new camper, but also bummed at the loss of my old camper.