I am having low and high alkaline phosphatase result. Ultrasound and X-ray report shows a healthy liver. What could be the cause?

Many sources. Alkaline phosphate is high due to multiple reasons. They get high due to problem in liver, bone or intestine. It's unclear if your level gets to normal. It will be wise to discuss with pcp.
Gall bladder. In addition to liver, alkaline phosphatase can come from the gall bladder, bone or blood. Slightly elevated levels could be a fluctuation in day-to-day simple metabolism or be slightly elevated because of who you are. It's a very non-specific test. Your physician should consider gather the appropriate information to ensure your liver is healthy and/or evaluate another source.