Yes, spleeter cut off super hight frequencyes due to the machine learning model try trained. Take a look to this coment for More information https://github.com/deezer/spleeter/issues/2#issuecomment-548798493
No worries, I actually just found one of them on the github here:
https://github.com/deezer/spleeter/blob/master/configs/4stems/base_config.json
You can see the F parameter in there set to 1024.
If you copy that file and name it "something.json" and edit the F parameter to your liking, you should then be able to do:
spleeter separate -i my_audio_file.mp3 -p "path/to/something.json" -o /output/path
and it will run with those customized parameters.
Not much computer knowledge needed to get started. It’s very straightforward if you are familiar with command line. Just follow their instructions page on GitHub:
https://github.com/deezer/spleeter/wiki/1.-Installation
If you want to train your own model, then you’d probably need some data science and programming knowledge.