52GB Movie Will Not Compress to Fit BD50

[Bullitt]

I have a full iso of a 4K UHD movie with a size of 52GB. After analyzing, the software repeatedly says no compression is needed after selecting the BD50 fit. It then lags and stays at 2% indefinitely. I have tried going back to default settings but that won't work either. Is there anything else to try ? Thanks

[Bullitt]

Working now, fails few times then works properly, I don't know why.