Assuming that your brushes there are world geo and aren't entities (make sure you're in group or object selection mode when you go to check. Solids selection mode acts like everything is world geo when you go to inspect the entity properties), it seems like your brushes are very large. Brushes tend to get broken when going over 8000 hammer units in one direction and can break at even smaller distances if the volume is large enough it seems. I would suggest splitting up some of the brushes into multiple smaller brushes with the clip tool and see if that helps.
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