Yes I noticed that too, when I was making cannons for the tanks and forgot to use the #flyspr-command, which I can't handle by the way. If modern war mod is ever to be made, MP40 wielding U.S soldiers will be shooting modded rocks or something...
Hmm, try
'#explspr <nbr>',
where nbr is between 10001 and 10238. 10200 is Curse, 10001-10012 is falling colors, some others are listed in the mod manual.
This might be enough, but might not. Illithids seem to only use this, but they have precision 100 anyway...
Latest Ashikaga version (2.4) does have the arrow sprites. My old version (2.0) which had the bug must have been from time before arrow sprites could be added.