Late reply, but better late than never.
Cracks at the foot of the guide happen because the metal foot of the guide doesn't bend as easily as the blank it is sitting on. This means that when the rod blank bends, the foot of the guide needs to be extremely well secured, otherwise it's going to lift a little bit away from the blank - even under a heap of thread and epoxy. And over time (can be a long time or a short time), cracks can start to appear at the end of the guide feet. As a rod builder, I have found that short standup game rods with roller guides are the most prone to 'feet cracking'. This is because the x-fast taper of the blank has heaps of bend, whereas the stiff metal frames of the roller guides have nearly zero bend.
Generally, I try and prevent feet cracking by making sure that the bindings are nice and firm and that the first coat of epoxy is thin enough to soak deep into the thread. I don't use less hardener or add thinners, but I do make sure that the first coat of epoxy is on the thread no more than 20 mins after mixing that particular batch, otherwise it becomes too thick and doesn't soak in well enough.