SHANGHAI—A crisis rocking a loosely regulated lending network is underlining the risks of a financing boom that has channeled Chinese household money into Hollywood movies and Wall Street deals.

Droves of teary-eyed investors from around China have descended on Shanghai Kuailu Investment Group’s swanky offices over the past week to demand their money back after the firm halted redemptions on wealth-management products for the roughly 250,000 clients of the firm and three affiliates.

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