I update mikrotik from some old 6.32 version to 6.49 and software works fine.then i click to update firmware and i get this problem.see the video
https://youtu.be/fAFRtfdkScc
Why this happen?
This is the second device in my network that I have broken and now I have to go to the field to reinstall with netinstall

I'm happy to test this on my SXT Lite 5, did you update both RouterOS and RouterBOOT to 6.49?

I have the same problem here.
I have bricked several devices upgrading the firmware to version 6.49. All devices are SXT.

I had two on the shelf I though I would test with. Upgraded both to 6.49 and firmware, so far both have been working just fine. Power cycled both of them multiple times after the upgrade without issue. Maybe this applies to a particular revision of the device? One was upgraded from firmware 6.48.2 other 6.48.4, i normally keep my spare equipment fairly up to date and tested.

I have upgraded a powerbox now and same problem: only recover device using netinstall. These version corrupts the bootloader sector

What ROS version did you upgrade from? What version was the firmware? I have upgraded dozens of different units for testing, including a powerbox. Only time I have had issues upgrading is a large version jump. On a unit that is way behind, I always update to the long term branch first. Update the firmware. Then go to a newer release. If it's super old, you can also download an older release from the archive and work your way up to help avoid boot problems. I always reboot devices before the upgrade to make sure max memory is available.

Facing the same issue, bricked 2 devices in my network both SXTLite5 , one upgraded from 6.47.X , other from 6.35.5, package update went well but after that upgrading the firmware in system/routerboard the s..t happend

All devices are with version 6.48.x and firmware on same version.

Same here.

I have a pair of two sxt lite5. The first that has near latest version (am not sure about the exact version) upgraded ros and firmware properly.

The other that has older version upgaded the ros without issues, but when i try to upgrade firmware, i lost it.

Is there any solution?

Did you send this to support?

If this is a global problem, we should keep this topic on top of the forum.

DO NOT UPDATE TO 6.49 UNTIL MIKROTIK GIVES OFFICIAL RESPONSE

Today we have two more bricks, rb2011. One of them bricked also with the latest bug fix without any config, only a dhcp client, (am not sure now the exact version).

We prefer to revert the latest version until mikrotik investigate this major issue.

We can provide any bug report or we can send the bodies to mikrotik!

Sended to mikrotik and no response at all.
Problem still continues ignored.

today i update groove from 6.40.8 to 6.49 and its ok but when i update firmware i got a problem again
which is lastest best working version without problem with security vulnerabilities?

You can load the backup bootloader to the Device. Then when it successfully boots you can use the force-backup-booter=yes parameter.
Or downgrade ROS and then upgrade the Firmware to that version.

To load the backup bootloader hold the reset button and only then apply power to the device. As soon as it powers up leave the reset button.

https://wiki.mikrotik.com/wiki/Manual:RouterBOOT

last best working version is 6.47.10 without problem

You can load the backup bootloader to the Device. Then when it successfully boots you can use the force-backup-booter=yes parameter.
Or downgrade ROS and then upgrade the Firmware to that version.

To load the backup bootloader hold the reset button and only then apply power to the device. As soon as it powers up leave the reset button.

https://wiki.mikrotik.com/wiki/Manual:RouterBOOT

And it is not solution for automated update methods. Mikrotik need to correct problem in a new FW.

You can load the backup bootloader to the Device. Then when it successfully boots you can use the force-backup-booter=yes parameter.
Or downgrade ROS and then upgrade the Firmware to that version.

To load the backup bootloader hold the reset button and only then apply power to the device. As soon as it powers up leave the reset button.

https://wiki.mikrotik.com/wiki/Manual:RouterBOOT

And it is not solution for automated update methods. Mikrotik need to correct problem in a new FW.

Who talked about automated update solution ? Not me.
The above steps can be used so that the device will boot, and then we can either downgrade or force the backup bootloader in order the device to work again.
Netinstall is not needed, as you describe in one of your posts.