"5100_D0MU075_D0MU445_D0MU845_Storage_Executive_fwbin.zip" is the latest/last firmware available so far.
I've been running this in production on a decent amount of 5100 ECOs/PROs and MAX SSDs for quite awhile.
Try updating the drive via the storage exec GUI with the zip above.
You'll need the Micron Storage Exec CLI - grab it from Micron's site.
You should back up any data you care about on the drive, and be willing to completely brick it.
Unpack the zip, you should have three folders and a "firmware.properties" file. This file will help you match the firmware to your drive type/capacity/controller. Copy the "1.bin" that matches up to your drive.
Then use the msecli to flash the firmware to the drive. HPE may have the drive locked, but the Dell drives gave me zero issues.
msecli -h list main help.
msecli -F -h will show you help for the firmware update process.
msecli -L will list all your drives.