Units disppearing in FoTS ambush

[Archy]

I ambushed a Nagoya army with Tosa, my army full and theirs almost full, and I cant win the battle since their spearmen (around 6 units) dont show at all. They are shown in preview of the battle but dont actually appear on the field. Im attacking and cant do anything but wait the timer out and lose. They arent shown at any point after I can see the enemys army. Despite not showing at the start of the battle in their very little and completely visible deployment area ive searched through the whole map and tried firing random spots with artillery but theyve just completely disppeared.

Im playing on legendary so cant load a previous save either. Auto resolving would have too many casualties and I still have a city to take after this battle. Cant do anything unless I solve this.

[Archy]

Noticed its not just their spearmen disappearing but three kachi spearmen, two levy spearmen, one katana, one kisho ninja and two bow kachis.