Installing a new Firepower image on Cisco ASA 5506 seems to take forever. Sometimes we get output to see that the process is still running, and sometimes not. I have actually recorded the entire process and shrinked down the progress from almost 2 hours to less than 4 minutes.
I think that watching this video will help anyone in the need to reimage FirePower to understand the different stages of the process.
Finally, someone who is experiencing the same thing I do, really informative video. I thought I was the only one having problems with reimaging.