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.
Is it possible you're one of the few with an incompatible control board? Can you post the start up sequence from the kernel log? Curious if you have neither 512 or 1024 mb like mentioned in the FW title.
Also, check and see if your control board says XILINX on it. If not, the AB FW is incompatible with your board.