You have a point, and I think there is a bit missing. Currently it says:
... impecunious operation of the bank could cause the value of the mortgages to be impaired just a tiny little bit at a time when people need most of the money in their checking accounts.
And probably should say something like:
... impecunious operation of the bank could cause trouble if the value of the mortgages is impaired just a tiny little bit at a time when people need most of the money in their checking accounts.
... impecunious operation of the bank could cause the value of the mortgages to be impaired just a tiny little bit at a time when people need most of the money in their checking accounts.
And probably should say something like:
... impecunious operation of the bank could cause trouble if the value of the mortgages is impaired just a tiny little bit at a time when people need most of the money in their checking accounts.