Unlikely that this is just random.

These credit facilities all have covenants and reporting requirements. When these things get frozen or wound down, almost assuredly some sort of risk covenant or similar was breached, which gives the fund manager the option of freezing or winding down the facility.

So how does an investor manage the risk? They vet the company (Greensill), and trust that its risk department / capital markets team can manage their credit facilities. In this case, it turns out that bet might've been off, but thats what happens in fintech investment sometimes.