The XMODEM file transfer protocol requires the communication lines to be transparent to all 8 bit characters, from $00 to $FF.
Set the appropriate parameters in the [Setup] Serial port dialog box. Data must be 8 bit, and Flow control must be hard (CTS/RTS) or none.
If file transfers fail, try connecting to the host with the binary option.
To connect with the binary option:
If file transfers still fail, please check that you have correctly configured and used the XMODEM command on the host side.
After confirming the above, take the log of the XMODEM transfer and send it to the Tera Term project.
Reference: Transfer the file via the intermediate server
The XMODEM file transfer protocol handles files in blocks of 128 or 1024 bytes, and file lengths cannot be exchanged. The received data length is always a multiple of 128 or 1024 bytes.
Sender puts padding in the last block that is longer than the length of the transmitted file. The padding is $1A according to the XMODEM specification. But it may be some other value depending on the XMODEM sending program.