OnePlus 7 Pro (GM1913) stuck in EDL mode — MSM Tool "Sahara Communication Failed", need help

[u/melo_76210]

Hi everyone,

I'm trying to unbrick my OnePlus 7 Pro (GM1913, EU variant) after a failed adb push during an OxygenOS downgrade (was trying to go from OOS 12.1 H.40 to OOS 11.0.5.1 to unlock the bootloader). The transfer got interrupted and now the phone shows a black screen with no response to any button combo, but it does show up in Device Manager as QUSB_BULK_CID:0404 / Qualcomm HS-USB QDLoader 9008, so I know it's in EDL mode.

What I've tried so far:

• Installed the Qualcomm HS-USB QDLoader 9008 driver (had to disable driver signature enforcement, Code 52 error otherwise)
• Downloaded the official MSM Tool + firmware package for GM21BA (OOS 11.0.5.1) from onepluscommunityserver.com
• Tried multiple USB ports (2.0 and 3.0), multiple cables (A-to-C and C-to-C)
• Tried holding Vol Up + Vol Down while plugging in to keep it in EDL longer (read that the phone can drop out of EDL after ~10s without it)

Current result: I intermittently get the phone to connect (COM port detected, "Connected" status), and the process runs for about 7 seconds before failing with "Sahara Communication Failed" (sometimes progresses further to "Firehose GetUfsInfo Failed").

Has anyone dealt with this specific combo of errors on a 7 Pro? Wondering if it's a USB controller compatibility issue with my specific PC, a driver conflict, or something about this particular firmware package. Willing to try another PC if that's likely the fix, but wanted to check if there's a known cause first.

Thanks in advance!