Yeelight LED Ceiling Lamp (YLXD12YL) firmware update failure

Have bought today Yeelight LED Ceiling Lamp (YLXD12YL), after installation and successful connection the device asked for firmware update. During the update the process has long stop at 90%, but few minuites later app on my smartphone showed me that lamp has latest firmware.
After that connection with lamp was lost (status in yeelight app was “Offline”). I removed lamp from device list and tried to connect it again, but each time I try to connect, the connection breakes at 6%, after that lamp continue blinking and one minute later stops blinking, and connection is not successfull.
Even if I turn on my lamp with switch, it has strange blink (it turnes off and then immidiately turns on) after one minuite of work.
What can I do? I think that something went wrong with firmware installation, is it possible to revert firmware update?

PS: unfortunately, I don’t know firmware version, as the device is no longer in my device list in phone app.

Update: today (01.10.19) when I came home I found out that second lamp has the same problems - offline mode even when it turned on, no reaction on remote controller, and blinking each minute. But 2 hours late both lamps became working. That lamp, that I removed from device list yesterday was succesfully connected, and works now without blinking, the second lamp became online, works without blinking and has connection with remote controller.

So, the question, what was that and how to deal with it in future?