I'd be leery of popping in another board. Assuming they are 3-volt boards, they should not be failing. Possible, but improbable, indicating that GRJ's point is well-taken. Nicks in wire insulation are sometimes very hard to find, and not visible unless you turn a wire over. Intermittent failures of some board-driven components are also hard to find.
If they're 5-volt boards, which are similar to 3-volt boards, it could be recurring natural death.