Red x's on files and folders in brand new My Passport Ultra

I just got a My Passport Ultra 5TB drive and I transferred a 103 gig folder with 20 subfolders and 550 mostly audio files overnight.

In the morning I didn’t see any error messages but a lot of the files and folders have red x’s on the file icons. I tried some random ones and they played with no apparent errors (they are 1-3 hour files though, so I didn’t listen all the way through).

I tried restarting the computer and unplugging the drive and plugging it back in. I also tried individually overwriting one of the files from the original but it still has the red x.

Has anyone encountered this? Is this something I should be worried about? these are irreplaceable files (10 years of my radio show) and i’m trying to clear space on my computer (my plan is to put them on this drive then back up the drive to the cloud) so i’m definitely nervous about deleting them before i’m sure they’re not corrupted.

ok well i’ll leave this here in case anyone encounters the same problem but i looked a few hours later and they all had green checkmarks! so i guess i just needed to wait. all told it was about 12 hours from when i started the transfer til they resolved (1 hour 40 minute estimated transfer time, i’m not sure how long it actually took).