I don't know is this a bug or is it protocol problem, but I cannot create new directory until copying operation ends.
I copy lot of files to different directories and while copying one file I want to create new directory, select new files and queue next copy process. But I get info "An error occured creating folder 'x'. Incorrect function". When copying process is finish, I can create directory.
My knowledge of the inner workings of MTP is only second hand but I think one of Jon's comments about the protocol is it only allows one action at a time, which may explain things.
What happens if you do similar using Explorer as a test?
(Either way, I usually recommend using an FTP or SFTP server on the phone over MTP as it tends to work better, and means you don't have to tether the phone to the PC via a physical cable.)
I'm mostly using FTP server on phone, but this time I want to use cable because this phone has slow download transfer (3-4 MB/s) and I was lot of files to copy.
I did not thikn about using Explorer. I always using Opus.
Maybe increase number of queue operations can be solution? Even manually set.
Next time I'll try to using Explorer or another Opus lister.
As I also use MTP for large/lots of files over years: No, you can't do more than one operation at the same time. To be honest, if it runs, just let it run and do nothing. MTP was always really crappy and I miss the real USB-modus for phones & cameras.