Well done for tracking down the lines!
I noticed the issue too and have reported the problem on the VBox forum already.
P.S. 0xA000 is nothing to do with fastload, it is just where the Main Menu is stored by E2B (address 20MB) for quick reloading of the Main menu.
Subject Re: Possible bug in latest VBox 5.2.8 triggered by E2B menu.lst