Failed to receive session end confirmation after successful BOOT upload

[ptesarik]

With heimdall v1.4.2, I'm getting this:

…
BOOT upload successful

Ending session...
[ 7.187929] [000066fe] libusb: debug [libusb_submit_transfer] transfer 0x557eea28c420
[ 7.187937] [000066fe] libusb: debug [add_to_flying_list] arm timer for timeout in 3000ms (first in line)
[ 7.187947] [000066fe] libusb: debug [submit_bulk_transfer] need 1 urbs for new transfer with length 1024
[ 7.187964] [000066fe] libusb: debug [libusb_handle_events_timeout_completed] doing our own event handling
[ 7.187970] [000066fe] libusb: debug [usbi_wait_for_events] poll() 3 fds with timeout in 60000ms
[ 7.188080] [000066fe] libusb: debug [usbi_wait_for_events] poll() returned 1
[ 7.188100] [000066fe] libusb: debug [reap_for_handle] urb type=3 status=0 transferred=1024
[ 7.188109] [000066fe] libusb: debug [handle_bulk_completion] handling completion status 0 of bulk urb 1/1
[ 7.188119] [000066fe] libusb: debug [handle_bulk_completion] all URBs in transfer reaped --> complete!
[ 7.188130] [000066fe] libusb: debug [arm_timer_for_next_timeout] no timeouts, disarming timer
[ 7.188142] [000066fe] libusb: debug [usbi_handle_transfer_completion] transfer 0x557eea28c420 has callback 0x7feaad735a50
[ 7.188155] [000066fe] libusb: debug [sync_transfer_cb] actual_length=1024
[ 7.188165] [000066fe] libusb: debug [libusb_free_transfer] transfer 0x557eea28c420
[ 7.188176] [000066fe] libusb: debug [libusb_submit_transfer] transfer 0x557eea2c4dd0
[ 7.188186] [000066fe] libusb: debug [add_to_flying_list] arm timer for timeout in 100ms (first in line)
[ 7.188207] [000066fe] libusb: debug [submit_bulk_transfer] need 1 urbs for new transfer with length 0
[ 7.188226] [000066fe] libusb: debug [libusb_handle_events_timeout_completed] doing our own event handling
[ 7.188232] [000066fe] libusb: debug [usbi_wait_for_events] poll() 3 fds with timeout in 60000ms
[ 7.288251] [000066fe] libusb: debug [usbi_wait_for_events] poll() returned 1
[ 7.288290] [000066fe] libusb: debug [libusb_cancel_transfer] transfer 0x557eea2c4dd0
[ 7.288651] [000066fe] libusb: debug [arm_timer_for_next_timeout] no timeouts, disarming timer
[ 7.288679] [000066fe] libusb: debug [libusb_handle_events_timeout_completed] doing our own event handling
[ 7.288691] [000066fe] libusb: debug [usbi_wait_for_events] poll() 3 fds with timeout in 60000ms
[ 7.288709] [000066fe] libusb: debug [usbi_wait_for_events] poll() returned 1
[ 7.288719] [000066fe] libusb: debug [reap_for_handle] urb type=3 status=-2 transferred=0
[ 7.288735] [000066fe] libusb: debug [handle_bulk_completion] handling completion status -2 of bulk urb 1/1
[ 7.288743] [000066fe] libusb: debug [handle_bulk_completion] abnormal reap: urb status -2
[ 7.288753] [000066fe] libusb: debug [handle_bulk_completion] abnormal reap: last URB handled, reporting
[ 7.288761] [000066fe] libusb: debug [usbi_handle_transfer_cancellation] detected timeout cancellation
[ 7.288771] [000066fe] libusb: debug [arm_timer_for_next_timeout] no timeouts, disarming timer
[ 7.288779] [000066fe] libusb: debug [usbi_handle_transfer_completion] transfer 0x557eea2c4dd0 has callback 0x7feaad735a50
[ 7.288787] [000066fe] libusb: debug [sync_transfer_cb] actual_length=0
[ 7.288797] [000066fe] libusb: debug [libusb_free_transfer] transfer 0x557eea2c4dd0
[ 7.288815] [000066fe] libusb: debug [libusb_submit_transfer] transfer 0x557eea28c420
[ 7.288824] [000066fe] libusb: debug [add_to_flying_list] arm timer for timeout in 3000ms (first in line)
[ 7.288834] [000066fe] libusb: debug [submit_bulk_transfer] need 1 urbs for new transfer with length 8
[ 7.288853] [000066fe] libusb: debug [libusb_handle_events_timeout_completed] doing our own event handling
[ 7.288860] [000066fe] libusb: debug [usbi_wait_for_events] poll() 3 fds with timeout in 60000ms
[ 7.352964] [000066fe] libusb: debug [usbi_wait_for_events] poll() returned 1
[ 7.353007] [000066fe] libusb: debug [reap_for_handle] urb type=3 status=0 transferred=8
[ 7.353020] [000066fe] libusb: debug [handle_bulk_completion] handling completion status 0 of bulk urb 1/1
[ 7.353032] [000066fe] libusb: debug [handle_bulk_completion] all URBs in transfer reaped --> complete!
[ 7.353048] [000066fe] libusb: debug [arm_timer_for_next_timeout] no timeouts, disarming timer
[ 7.353064] [000066fe] libusb: debug [usbi_handle_transfer_completion] transfer 0x557eea28c420 has callback 0x7feaad735a50
[ 7.353076] [000066fe] libusb: debug [sync_transfer_cb] actual_length=8
[ 7.353086] [000066fe] libusb: debug [libusb_free_transfer] transfer 0x557eea28c420
ERROR: Failed to receive session end confirmation!
Releasing device interface...
[ 7.353143] [000066fe] libusb: debug [libusb_release_interface] interface 1
…

And, indeed, my phone does not terminate download mode and shows: "Downloading... Do not turn off target!". The progress bar is at 100%, though, so I believe the flashing itself was successful.