The knowledge in this community is simply amazing.
Many many thanks, Perrin, and thanks eclark -- it looks like both mason caching and innodb 'stale data' were occurring -- we're not mason experts, but the mason issue seemed to revolve around the difference between code in <once> blocks vs. <init> block, and yes, also, innodb was showing 'old' data to the second client as it hadn't committed in a while.