Shlishi “As far as information, you must always ask a shaila before giving any negative information.”
You must also always ask a shaila before WITHHOLDING any negative information. There are situations where one has a chiyuv to tell over information with regard to a shidduch, and situations where it is assur. There is no such thing as to err on the side of caution — you must always ask a shaila.
Although I certainly don’t think it is the “main” cause of divorce, there is a definite number of divorces that occur when information that should have been told before the marriage was withheld and only came out afterwards. (This is particularly true with “quick” divorces.) Had this information been known, the marriage would not have taken place, and obviously neither would the divorce. (I have first hand knowledge of two such cases, one where the divorce took place about 7 weeks after the marriage with the full encouragement of Daas Torah, and the other which took place a few months after the marriage, with the added tzaar of a child on the way. . .)