This question here gives the probability of such a value, called a "fixed point" existing as 63%:

https://crypto.stackexchange.com/questions/68431/cryptographic-hash-where-the-hashing-function-input-is-similar-to-the-result

There is at least one such "fixed point" value found for the SHA256 algorithm. An example is here:

https://crypto.stackexchange.com/questions/48580/fixed-point-of-the-sha-256-compression-function

As explained in that question, "[e]asy to find fixed-points are a known property of this construction", therefore this isn't a problem.