Poppa,
I am not really sure what the problem is, it is a very slow leak. Pretty sure it is not a yucca. I have quite a few of those, but they are easy to see and avoid. I suspect a type of cactus that is very low growing and has about a 1" thorn. Good thing is the thorns are not very stiff, so the tires tend to just bend them, but on some of the older plants, the thorns are a little stiffer. I noticed several of these types of cactus had stuck between the treads on my R4's. I think the rear tires are thick enough to withstand the thorns, but front tires are thinner. Did you get the R4's?
I am not really sure what the problem is, it is a very slow leak. Pretty sure it is not a yucca. I have quite a few of those, but they are easy to see and avoid. I suspect a type of cactus that is very low growing and has about a 1" thorn. Good thing is the thorns are not very stiff, so the tires tend to just bend them, but on some of the older plants, the thorns are a little stiffer. I noticed several of these types of cactus had stuck between the treads on my R4's. I think the rear tires are thick enough to withstand the thorns, but front tires are thinner. Did you get the R4's?