SanDisk Glide: Low transfer speeds

I just got a SanDisk Glide USB 3.0 128gb stick as an RMA for my ultrafit 128 (overheating to the point of burning with slowing transfer speed). But I’m having the same issues as my ultrafit drive, Overheating but not as bad, and slowing transfer speeds. I get 40-50MB/s for 10-15 seconds, then drop down to 10MB/s for the rest of the large file transfer 700MB+ files.

Question is, how can I keep the drive from droping transfer speeds? I paid for USB 3.0 speeds, not overall sub usb 2.0 speeds. Or should I just demand my money back for the cost of the orrigonal drive and return the new stick and buy another brand?