The reason behind a failed call can be manifold.
Do not assume that the error message is coming directly from the called contract:
- The error might have happened deeper down in the call chain and the called contract just forwarded it.
Also, it could be due to an out-of-gas situation and not a deliberate error condition:
- The caller always retains 63/64th of the gas in a call and thus even if the called contract goes out of gas, the caller still has some gas left
- Many Reasons
- Error -> Called Contract Cannot Assume
- Error -> Deeper Call Chain Callee Forwarder
OOG(Out Of Gas)- Caller -> 63/64th Gas