All files copied were under 500 MB in size each, guaranteed.
No dmesg entries from around the copy failure time.
Syslog reveals this:
Jan 13 19:46:06 eagle ntfs-3g[4262]: No free mft record for $MFT: No
space left on device
Jan 13 19:46:06 eagle ntfs-3g[4262]: message repeated 40 times: [ No
free mft record for $MFT: No space left on device]
Jan 13 19:46:06 eagle smartd[988]: Device: /dev/sdb [SAT], SMART
Prefailure Attribute: 1 Raw_Read_Error_Rate changed from 81 to 76
Jan 13 19:46:06 eagle smartd[988]: Device: /dev/sdb [SAT], SMART Usage
Attribute: 190 Airflow_Temperature_Cel changed from 64 to 65
Jan 13 19:46:06 eagle smartd[988]: Device: /dev/sdb [SAT], SMART Usage
Attribute: 194 Temperature_Celsius changed from 36 to 35
Jan 13 19:46:06 eagle smartd[988]: Device: /dev/sdb [SAT], SMART Usage
Attribute: 195 Hardware_ECC_Recovered changed from 81 to 76
Jan 13 19:46:06 eagle ntfs-3g[4262]: No free mft record for $MFT: No
space left on device
Jan 13 19:46:15 eagle ntfs-3g[4262]: message repeated 3154 times: [ No
free mft record for $MFT: No space left on device]
Is it some kind of NVMe temp garbage overhead?