If you run a embedded Linux PC like raspi often some Linux Commands fail without error messages, cause the hardware performance is low tech.
Same i have seen on the split command..
to split a 50GB Photos-Archive File to 4Gb on a USB Drive i found out that:
sudo split -b 4096m -d -u Photos.tgz Photos-Archive_
fix the job..
Cause option -u disable IO-Caching over the 2.0 USB Port to the RAM of the raspi that the Data of the Output Stream is written direct to the Drive.