Bill, same here, as I use it exactly as you describe. I found E's very sensitive to voltage drop and line
noise. I ran a direct cable from bat to the display, installed magnetic braker protection and ferrites for noise reduction, and finally removed Seatalk power distribution from it (now ST 60 are powered independently, and E120 wired for data only). The problem reduced dramatically, and now it appears rarely (once in a week sailing). The same happened to my old E80 (3 years ago).