metastability
Metastability is the state where your logic behave irrationally. Sometime you get what you want, sometime you dont. Typically happens in the case of two signals changing at the same time. Watch out for the situation.
To sync two clock domains, you will have to sync the slower one with the faster one. i.e "sample" the slower on with faster (using a D-FF or so). alternately, you can use a faster third clock to bring the two into one common domain.