As far as I know in the documentation there is no mention that the Hugo binaries are meant for use as portable apps or that Hugo projects can be served through USB sticks.
What you describe sounds like typical I/O issues one encounters, when running apps through USB sticks. Hugo projects are not meant to be run from USB sticks, FAT32, NTFS or whatever. When one runs hugo server then everything is served through memory. Using a USB stick will give you subpar performance.
Also regarding the other comments in this thread, may I remind to all of you that you really need to provide specific steps to reproduce what you describe including sharing the code of your projects.
There is a big pink banner at the top of this forum with the guidelines about requesting help. Also just in case the banner got dismissed, the guidelines are always available over here: https://discourse.gohugo.io/t/requesting-help/9132