I've got a 10SI at the console and a 9DI upfront, never had a bit of trouble with that 10 at the wheel, but that 9 upfront has been a total cluster the whole time. It's flush mounted in the bow (2016 Ranger), and about 50% of the time works fine, but the other 50% it'll read 874 feet deep, 369 degree water temp, and occasionally will just get screen interference. Seems to do it mostly in shallower water, but will do it no matter the depth or bottom composition. I've grounded my trolling motor, you name it. I also installed a heading sensor puck, which I intended to flush mount at the bow too, but had to put it next to the console because of electronic interference. You can run a magnetic compass all over the front 3' of my bow and there's interference coming from somewhere.

Well, my niece's fiancé is the main "rigger" at Wedowee Marine (maybe the biggest Phoenix dealer in the state), that rascal is a wizard with these electronics. So back at Christmas I was lamenting to him about all this and without knowing, he asked, "You got Humminbirds, right?" I said yes, and he said, "live with it, you ain't gonna fix it." Apparently this is a widespread issue.
He did say I could probably get the new Ultrex with the built-in transducer and eliminate all/most of it, but most likely nothing else would work.