Ben,
We can learn together about this wood...Glad you posted your findings...As said, it may be a characteristic of this wood...On a side note, if it were mine, I would size that back 2 times with some hide glue allowing it to gel and fill the gaps and lay some sinew down...You done a fine job following the grain...Real hide glue is some super stuff, I use it for cracks instead of super glue...It will pull the wood fibers away before breaking under tension...I found knox to be a little brittle because it is so refined...Don't want to start an argument here about hide glue vs knox, some will say it's the same, but it's not...Please keep me posted on your findings with this Live Oak...
Don