In version 0.74.3, invoking int 15h with ah=86h often results in a bunch of "Illegal read/write" messages.
This seems to have been fixed a long time ago in trunk with https://sourceforge.net/p/dosbox/code-0/3731/ , it's a simple missing break in a switch, but somehow it apparently didn't make it into a release.
People complaining about this bug on StackOverflow: https://stackoverflow.com/questions/43194265/dosbox-is-buggy-with-int-15h-ah-86h