SL8082T stuck at boot loader

I started re-flashing the modem for a new FW by updating boot loader first. Boot loader most propably was not fully flashed because it seemed that download was for some reason interrupted.

Now modem seems to be stuck at boot loader mode. At boot loader mode it should be possible to start the download mode, but a AT+WDWL gives an error. I guess that what I need to do is start download mode and use XModem to retry downloading of the boot loader? How that is done if download command is not accepted?

I am using USB connection to the modem and RTS/CTS is on.

Here is how it behaves:
at
OK
at
OK
ati
Manufacturer: Sierra Wireless, Incorporated
Model: SL8082T
Revision: S4_1_0_7AP R1431 CNSZXD00000155 2012/11/19 16:06:52
IMEI: [imei of the modem]
IMEI SV: 9
FSN: CEM0504491430
3GPP Release 5
+GCAP: +CGSM,+DS,+ES

OK
at+wdwl
ERROR

I think that you can save your module by using the cwe files with the binary updater, download it here:
http://developer.sierrawireless.com/~/media/Support_Downloads/AirPrime/Software/Firmware/R7.52/R7.52.0.201404040850.SL808x.ashx

Thanks. This starts downloading, but can not complete it. I most probably have USB cabling issue with this prototype board.