Is there any way to fix this?
No. (But apparently there's a way to lessen the delay a bit.)
If you read the threads on the issue, you'll discover that you and others in your situation should "learn how to read" or something to that effect, whereas in fact at the
start of instructions for installing raw on the 5d3 there should be something like this:
Under no circumstances begin installing raw on your 5D3 until you have read thiswith a link to a description of the bootflag issue on the 5D3, the effects it has, the fact that most aren't bothered by it but some may some have concerns, any information about the nature of the problem and the prospects for a future solution that the devs are willing to divulge, a reminder not to nag devs about when a solution will be forthcoming, etc.
That would have allowed you to make a choice as to whether or not getting the truly amazing raw capabilities on your 5D3 in light of all this is worth it for you. But you didn't get that choice.
People have suggested repeatedly in the threads that better warnings be posted to help prevent this sort of thing from happening, and for the life of me I can't understand why it hasn't occurred.