I had a similar issue with the bash bunny not upgrading and getting very hot. I looked at the downloaded file and noticed it was named 'ch_fw_1.3_264.tar' after downloading. Based on the download site it should have a name of 'ch_fw_1.3_264.tar.gz'. I renamed the file to now have .gz extension and then placed it on the bunny and it upgraded fine. Let me know if this also works for you.