Also have the same issue 3 year old 10" Skyview red x out on number 1 EGT. engine start comes on perfect, no x out. after 3 flights no issue all EGT's working. Update Dynon 15.3.3 software, red x out on number 1 EGT comes on again. Inspect all grounds, all good. Dynon told me the same things about checking connections. Visiting their booth at Oshkosh for further discussion.
Mark C. 119RV.