dsc,My wife would call that "döhävet". Try pronouncing that
The bread looks lovely otherwise though. You probably know by now if it was only because you cut it too soon: many breads need their rest before cutting them. If it wasn't and you got parts/blobs of un-raised dough, you may have used old yeast or maybe you heated the yeast up too much when mixing it in - or perhaps it wasn't mixed into the dough good enough.
It's a lot like the "channelling ghost" of espresso; can be difficult to analyze and harder to root out.
I don't like the taste of those parts, maybe some others here do, but for me - no thanks. Tastes of yeast, and feels like chewing half-dry dough.
It looks like it was just a little, though. A little is usually fine, you can cut it off if it is too much to eat.
P.S. I am off bread and other carbs since... what is it, over a year now? So I haven't baked any for a long time. I do miss those sourdough breads... can smell them as I see those pictures. Thanks for sharing people, especially Zapty Zourdough! D.S.
P.P.S I have never used a baking stone. Is it really that good? D.D.S.