SYS.COM caused issues with NetDrive images due to a bug in DOS 3.3’s SYS command. The command changed the BPB in the image’s first sector, corrupting it. This was a result of DOS 3.2’s “Generic IOCTL” function not being supported by NetDrive, causing SYS.COM to write incorrect data. The bug stemmed from SYS.COM not checking the return code from Generic IOCTL properly. This controversial bug negatively affected hard drive images but not floppy disk images. The author, Michael Brutman, dissected the issue thoroughly, pointing out the flaw and its implications, shedding light on a lesser-known bug in DOS operating systems.
https://www.brutman.com/Adventures_In_Code/DOS_33_SYS_Bug_Hunt/DOS_33_SYS_Bug_Hunt.html