MongoDB server fetches the key from the session statistics cursor here. On big endian system this key is not in the expected form.

e.g. On a little endian system a key 4000(0xFA0) is returned like this:

The key returned by WiredTiger stats cursor: 93823560585120 (0x555500000FA0)

Whereas the same key on big endian system is like this:

The key returned by WiredTiger stats cursor: 17180800459888 (0xFA037822470) 

Investigate that why session statistics cursor returns the incorrect correct key.