OK, over an episode of The Expanse (!) I've figured it out. There seems to be a unique inability to link a thought with AggData (https://www.aggdata.com/) as a child of the thought Marketing (https://en.wikipedia.org/wiki/Marketing). I can't figure out any logic to it. AggData links to other thoughts just fine, as does Marketing. In another test brain, the two link together just fine.
Totally weird, but I disconnected that link and kept it under an intermediate child thought of Marketing. No idea what that's about but it seems to have solved the issue by avoiding it. Something about those two thoughts in this particular brain at that particular location. Even adding those two thoughts in a different location in my megabrain did not cause issues. Weirded out, but issue closed i guess. Jim
TB8022 32bit Java 32bit Version 8 Update 141 Firefox, Office 2013 Pro Plus 32bit 64bit Win10Pro 64bit Primary Laptop, 8GB RAM, Intel Core i7 64bit Secondary Laptop, 64GB RAM, Intel Xeon E3 Brain user since zygote