I just bought an Ultra Flair 128 GB. I see slow downs too, but not as bad as others. I have tried several times with different formatting. What I see is that for the first 2 GB of transfer, it writes at 70 MB/s. after the first 2 GB, the write speed slows down to about 30 MB/s +/- 3 MB/s with no further slowing.
I am disappointed with this very reproducible slow down. I am a long time satisfied SanDIsk customer going back over a decade with many SD cards and CF cards. I chose this USB drive because of my past positive experience with SanDisk products. So I am quite disappointed with the slow down and this thread has no plausible fix.
