Hi Paul, as you probably know the modules need to be built against exactly the same kernel they are to be loaded to. Those error messages point to this not being the case. Some possible reason for this is Yocto building the kernel but using a cached version of the target image that do not include the new modules.
Could you paste the output of modinfo run against both one of the modules already loaded in the kernel (check lsmod) and then the failing modules?