Looking at where the crack is and your comment combined made me think, that join pretty much hold the weight of the saucer and neck assembly as well as the upper half of the engineering section, a rather large chuck of the model in fact, so if the seam was to fail it would be the natural place. Add to that the extra weight of electronics .... I wonder if theres ways of preventing it in the early stages of construction. The other option is addition supports for the saucer which really detracts from the model as a whole.

I'm keen to see how you handle the repair and hopefully it will last.

By the way, 9 pages here and 9 pages on SSM  ;D freaky