Einstein was so incensed by the manner in which quantum physics appeared to offer a place for randomness within the universe rather than the smoothly mechanistic model he favoured. He and two colleagues proposed the ERP 'thought experiment' that he believed could demonstrated the falsity of quantum physics.
Unfortunately for him Bell's Theorem came along and no one has ever been able to falsify that particular set of equations.
In essence the problems is that if Bell's Theorem is true (and to date it seems as unshakable as any theory in science) one of the following conclusions must follow.
1 Relativity is false
2 Quantum physics is false
3 Locality fails
4 We live in a series of parallel universes in any one of which completely different events take place
5 The universe we experience is a creation of the individual observer and has no 'objective' reality
6 Our interaction with objects on the purely mental level can affect them physically
7 The speed of light within the universe is NOT constant as Einstein believed and it IS possible for objects to travel faster than light
8 An exchange of information between particles might take place at a speed greater than that of light
9 Everything within the universe is intimately and interdependently interconnected with everything else so any action from no matter how remote a distance can affect particles on the other side of the universe
10 The universe is a gigantic hologram and one piece of it is an exact mirror of all the others
All these theories have merit as well as difficulties.
To me the most likely solution is that more than one theory will be required to reconcile relativity and quantum physics but the postulation by an increasing number of theoretical physicists of 'tachyons' - particles that have never been observed and which many physicists believe are incapable, even in principle, of being observed and yet which have as their principal notional property the ability to travel faster than light suggests strongly that Einstein's belief that the speed of light is a constant may be mistaken and perhaps that is the most fruitful place to begin remodelling the two theories.