I noticed many are complaining on sticky keys in dosbox this generally happens with any big delay game.

solution is to edit your dosbox-shared-single.conf in your game directory and add
mode con rate=24 delay=2
inside the [autoexec] portion before the game launches.

like so
[ipx]
# ipx: Enable ipx over UDP/IP emulation.

ipx=false

[autoexec]
# Lines in this section will be run at startup.
# You can put your MOUNT lines here.
mode con rate=24 delay=2

This will fix your repeat keystrokes and make the game very much more playable.