"Firmware corrupt" on every os version

Hi, I have problem with update/downgrade flyme os on my meizu mx4.
After my device was updated to terrible, I decided to downgrade os back to 4.x.x.x but I cant do that because of “Firmware corrupt” message.
I tried almost every stable versions of flyme 4.x.x.x ofcourse with checked “Clear data” option but every time same error message.
Can you help how to finally downgrade flyme os ?
Thank for reply.

i have problem with that 2, even when i tryed 5.1.8a, anyone help?

Looks like your connection to Meizufans was lost, please wait while we try to reconnect.