I know the existence of this town Dalmanutha has been disputed as well as seeking determinations in the Aramaic, and geography as it was some 2,000 years ago,etc. But there are two factors involved in Mark 8:10 and Matthew 15:39. Both references say that Jesus went to the 'parts' or 'district' of these two towns.
The articles do not bring out the 'area' reference relative to the cities of Matthew and Mark.
They were close together and both writers wrote from their own perspectives. One says the 'area of Dalmanutha' and the other the 'area or district of Magdala.' These were harbor cities with boat multiple boat landings in each district (I have seen the 2,000 year old boat uncovered on the shore area in the region under discussion) for commerce. I have been there. It would be impossible to say at the exact point they came to the shore so each writer told their readers it was in the area of this city and the other in the area of this city. Both cities must have been known then by their readers,but each wrote to a broader audience also beyond Palestine; so placing both city locations together as an 'area' or 'parts' it showed approximately where the boat landed. Mark in his experience may have been more familiar with Dalmanutha and Matthew was more drawn to use- based on his knowledge- Magdala as his reference point; but neither would or could pinpoint the specific landing location for this particular boat journey then; so somewhere between these two towns to give a geographical perspective.
In one place the gospel writers say' in the area of Tyre and Sidon' towns known then or two thousand years ago and today thanks to excavations. Since the exact location could not be shown (today a writer could use photos) two cites that were close to each other gave the early reader a picture of where the event took place.
Some have thought that both cities then were known by those two names. Not a first in history. Some still call Vallejo Water Town in the past but others for the most part it is Vallejo- a N.CA city.
For there to be a real contradiction there must be no way to reconcile the opposite observations or views.
I can tell you that in Hebrew certain OT references refer to the earth as circular. I have and just sharing studied Hebrew and Greek since 1963 and have a great many lexicons. I love these two languages and have spent countless hours studying them.
In one reference only as point of interest- Jesus refers to an event that is worldwide where some experience this event at night and others during the day time at the same time. This is an indirect reference to the earth being spherical and that it rotates creating day/night on each area/side of the earth -something we moderns take for granted based on to date knowledge
I am not a JW, and would never ascribe to many of their cultic beliefs. They can teach and do as they please though based on free speech principles. I think we each determine truth for ourselves.
Thanks for your good and forceful comments. At least you have solid convictions!