Dozens of former artificial intelligence researchers from Google who struck out on their own are learning that startups are tricky.

The latest example is French AI agent developer H, which lost three of its five cofounders (four of whom are ex-Googlers) just months after announcing they had raised $220 million from investors in a “seed” round, as our colleagues reported Friday. The founders had “operational and business disagreements,” one of them told us.

The drama at H follows the quasi-acquisitions of Inflection, Adept and Character, which were each less than three years old and founded mostly by ex-Google AI researchers. Reka, another AI developer in this category, was in talks to be acquired by Snowflake earlier this year. Those talks, which could have valued the company at $1 billion, fell apart in May.

AI image developer Ideogram, also cofounded by four ex-Googlers, has spoken with at least one later-stage tech startup about potential sale opportunities, though the talks didn’t seem to go anywhere, according to someone involved in the discussions. (For those interested, a longer list of AI startup takeover targets can be found here.)