B737 MAX 8 Captain reported a distracting high pitched tone on descent that led to being high on a fix. With the help of Maintenance; the Reporter discovered the problem may be caused by the ground crew's unsafe plug removal procedure.

Narrative

After being cleared direct to ZZZZZ on the arrival and cross it at 11;000 ft.; we encountered a high pitch tone that had been building up after departing ZZZ [Airport]. Due to the high pitch tone encounter and late crossing restriction clearance; we arrived at the fix a little high. I contacted Maintenance the next day to find out the origin of the tone. It appears there could be a safety issue with the ground crew plug-ins on the MAX. Due to the height of the external jack; some ground crews use the nose gear access. Instead of pulling the cord near the base of the plug; it's pulled from several feet away; which breaks the tip of the plug off in the access. This creates a build-up in static noise; eventually becoming a high pitch tone. This causes a major distraction to crews due to the level of noise; making it difficult to communicate between crews and ATC.Aircraft malfunction caused physiological distraction due to high pitched tone. Recommend training for the ground crew regarding the plug removal technique and the potential for a safety issue.