Only over 7 years to get back to this but better late than never.
I've got the originals somewhere so if I find them Ill post screenshots but maybe it's a funny DOS driver issue.
I've put a picture showing 3 images of the video from the disc version on Dosbox.
Starting clockwise it is the high res video whcih has scanlines, quarter video and I think editing the ini file to deinterlaced did this as well and last was using dosbox scaler* to enlarge the quarter video.
I've put some markings to show the screen shapes as they aren't the same size when putting the game into fullscreen.
You can't deinterlace the videos in this game, what GOG did was just to fix (tweak) the old winxp exe that Trilobyte got out a few years back before it went out of business. Those executables had the problem that on newer machines they ran too fast, GOG fixed that but we're stuck with interlaced video because that is how these executables were in the first place, also no spooky mode available, sorry! GOG, I guess you're owing us this fix in the future!
With the discs and that exe the animations run too fast but the rest of the game plays almost normal. The sound and music were better and slightly changed.
I had the same problem with Dosbox but setting the core to normal almost fixes it.
* from dosbox wiki conf section.
scaler = none | normal2x | normal3x | tv2x | tv3x | rgb2x | rgb3x | scan2x | scan3x | advmame2x | advmame3x | advinterp2x | advinterp3x | 2xsai | super2xsai | supereagle | hq2x | hq3x
Specifies which scaler is used to enlarge and enhance low resolution modes, BEFORE any additional scaling done according to the Fullresolution and Windowresolution settings under [sdl]. To see comparisons between the different scalers, see Scaler.
none: no scaling is performed.
normal: nearest-neighbour scaling (big square pixels).
scan: like 'normal', but with horizontal black lines.
tv: like 'scan', but with darkened versions of the data instead of black lines.
rgb: simulates the phosphors on a dot trio CRT.
advmame: smooths corners and removes jaggies from diagonal lines.
advinterp: identical to 'advmame'.
sai: similar to 'advmame' but with much softer color gradients and edges.
supersai: similar to 'sai' but sharper.
hq: a 'high quality' scaler which delivers a cleaner and sharper image than 'advmame' or 'sai' scalers.
Default is normal2x.
Supported scalers which still need descriptions: supereagle