I'm not using any third-party solutions other than DOSBOX as per default installation, and my OS is Windows 7 64-bits. Ultima 8 seemed fine for the first hour or so, but as I left the city of Tenebrae, I started to see guardsmen talking to themselves nonsensically; I had trouble having a conversation with a NPC who refused to stop wandering round her house, often times far away from my character; the ghoul in the caverns beyond the Torax farm was talking to itself, mostly guard chatter such as "move along" and "don't get into trouble" et cetera. Also, some of the textures flickered quite a bit.

Anybody else experienced these problems? Is there a permanent solution?

Nevermind. I found Pentagram and it seems to have corrected all of the issues I had experienced.

However, if you know of a better solution and/or problems with Pentagram, let me know. :)

ON A SIDE NOTE: After much tinkering, I managed to configure Pentagram to work correctly with my 21:9 Ultrawide monitor. .INI file below:

[pentagram]
defaultgame=u8
fullscreen=yes
scalex=569
scaley=240
scaler=point
width=2560
height=1080
bpp=32
tff=no
midi_driver=windows
skipstart=no
textdelay=8

[u8]
path=C:\GOG Games\Ultima 8\ENGLISH
lastSave=