This failure mode suggests that the term "Solid Wood" was used quite loosely when describing this doweling. It is solid wood in the same way that chipboard is solid wood - all the constituent parts were solid wood before they were glued together.
Oh well, back to the drawing board.
In other news I discovered today I had been shortlisted jointly with the DCMS Safety Tech Team for a "CogX Global Leadership" award for the we've been doing on/for the Online Safety Tech sector. We're in some pretty illustrious company there so I don't have high hopes of winning, but it's nice to be even considered!