More than likely the problem is not with the type of magnesium but the status of the other electrolytes. If sodium is lowered then magnesium is likely to push it down further, same with potassium. Both sodium and potassium are also electrolytes and play key roles in the body. If you test with a hair analysis lab they can identify potential problems.
Calcium is antagonistic to magnesium and vice versa, so if you have high magnesium intake, it can push down calcium. As a side note, many people are calcium heavy so it may not be an issue. Vitamin D should also be checked since it plays a key role in magnesium utilization.