It is not clear to me what this would be, but I would proceed with caution as ignoring a "bad read" might result in corrupted code on disk (it doesn't have to it as the check could be faulty).
First thing to do is trying a different USB port, especially downgrading to USB2 if you used a USB3 port before.
The other thing you can do if you have a machine with VirtualBox or other VM, is to install from that USB to a VM and see what happens.
If you have the time to buy another stick, do so and weigh the cost of spending against potential future trouble. You can of course re-use the stick for other things if it turns out that gives the same error (indicating it is something in the target machine) ¹.
If another stick gives the same error, it might be some USB problem or a memory problem. In that case test the memory extensively (memcheck) even if you tested the USB on the target machine (from an older installation e.g.) as it could be that the installer media check hits some other memory with a bad spot that the "manual" check doesn't hit.
memcheck doesn't show anything, I would try a more minimal network installation if available. It might just be that the USB interface goes bad after reading a certain amount of bytes.
If you decide to proceed, it might be that you get more errors (if the USB hardware has some errors), but AFAIK the checksums of the individual packages will still be checked during the installation as well independent of the "global" media check.
¹ Reusability is the primary reason I use a SD cards for installation, as I can also use those in my camera, phone and ebook readers. I did find however that my laptop did not boot from my multi-card USB3 reader (with hub, from which my desktop PC and servers boot fine). My laptop would only boot from my single card USB2 SD card reader