Hmmm... I wonder if there's a configuration you can add, the dosbox doesn't specify it in the conf file so...
Note: Taken from Ultima Trilogy conf file.
[dos]
# xms: Enable XMS support.
# ems: Enable EMS support.
# umb: Enable UMB support.
# keyboardlayout: Language code of the keyboard layout (or none).
xms=true
ems=true
umb=true
keyboardlayout=auto
so
Keyboard Layout information...
But that's assuming it's not a problem with windows 10. It's entirely possible Dosbox needs an update to be compatible, or windows 10 has bugs so it's not feeding to the SDL correctly on DosBox... either one could be right, i don't know yet... i guess look for bug reports...
edit: Actually
found a related post where they recommended a solution
from here.