Proxmark3 fullimage not flashing because of Lock Bits, but bootloader works!

Are these the mothods you have tried?

Where did you get your PM3 from?
What guide did you follow to set up your PM3?

I have found that sometimes, a fresh install can be faster and less painfull than fault finding.
Thats what I would do if the issue persists

I would follow one of these
Full and complete instructions

Abridged version
https://forum.dangerousthings.com/t/handy-dandy-tips-and-tricks/13041/14?u=pilgrimsmaster