Can't get TeraTerm to truncate padding on last packet of YMODEM transfer - Tera Term Ticket #39181 on OSDN

I've been writing a YMODEM file sender for the Arduino, and it's all working, except that when I send a file from my Arduino to TeraTerm using YMODEM, the resulting downloaded file retains all the padding characters in the last block, regardless of whether I use 0x00 or 0x1A (as suggested in the YMODEM documentation from many years ago). If I compare the transmitted file and the received file, they're identical down to the start of the padding in the final packet. I've tried various things, such as sending the first packet with "filename 0x00 filesize 0x20" (again as the protocol seems to show), but I always get that last chunk in the received file. I've duplicated the example 67-byte file shown in the TT YMODEM documentation in terms of block size, separator characters, etc, but no luck. Any suggestions?