Are you using the sonar chart or the nautical chart on your phone App Tim? The sonar chart is much more accurate than the nautical chart. You also have to update your navionics card in your sonar unit yearly as the sonar charts change due to anglers uploading their data. Most anglers don’t update their charts or their firmware on their unit and they are constantly updating those things. Navionics on Lewisville used to show all kinds of structure that isn’t there. My last few updates increased my map accuracy 10 fold and the new maps no longer have that ghost structure. I know Lavon maps have been off by 10 ft on the deep part of the lake. I’m wondering if you update your map if it will correct your problem.