I upgraded to the 2017 firmware and then tried the 2018 firmware after and I get an instant error message saying its the wrong file type or something along the lines of that.  I know the R4s can be a bit fragile and every time i try to upgrade my board temps go crazy and it scares me a bit. It takes my R4 a few minutes before the fan really starts spinning every restart and the chip readings will hit the 90s. I think ill just keep the adjustable MHz version for now. I like to keep it on the lowest setting to keep board temps to a minimum.