For some reason, the X/Y-modem protocol handling is messed up on the last packet when using the decompression feature (-d), and minicom will hang instead of closing the upload window. Pressing ESC will get back the RedBoot prompt (possibly with a RedBoot error/warning), but the data appears to have decompressed fine. This can be verified using the 'cksum' command if critical.
Created attachment 41712 [details] patch to strip extra ^Z characters at end of buffer
X-modem pads the final data record with ^Z characters. The attached patch strips them (if it finds at least 3 consecutive ones at the end).