The fix is:
Try commenting out line 233 in InteractionBehaviour.cs so:
#if UNITY_EDITOR
if (_contactMode == ContactMode.GRASPED && UntrackedHandCount == 0 &&
Vector3.Distance(_solvedPosition, _warper.RigidbodyPosition) > _material.ReleaseDistance * _manager.SimulationScale ||
Quaternion.Angle(_solvedRotation, _warper.RigidbodyRotation) > _material.ReleaseAngle) {
_manager.ReleaseObject(this);
}
#endif
becomes
#if UNITY_EDITOR
if (_contactMode == ContactMode.GRASPED && UntrackedHandCount == 0 &&
//Vector3.Distance(_solvedPosition, _warper.RigidbodyPosition) > _material.ReleaseDistance * _manager.SimulationScale ||
Quaternion.Angle(_solvedRotation, _warper.RigidbodyRotation) > _material.ReleaseAngle) {
_manager.ReleaseObject(this);
}
#endif
Note that even without this fix, grabbing and holding should work in a build.