Playing as Baktria - siege on Taksashila lifted

Definitions
Taksashila: The northernmost of the Indian cities, in the province of Gandhara.
Next turn button: The button in RTW interface that advances the game to the next turn.

Creation/Duplication
(As Baktria) I sieged Taksashila and built 15 sapping points. I waited for the city to surrender/sally (which is to happen on year 258 BC). The bug occurs when I am at the very last turn before the city must fight or surrender, immediatly after I press the next turn button.

I re-loaded the game (had saved just prior to the end of the turn) several times and this happened every time. I tried queuing more siege equipment, I tried adding a mercenary unit to the besieging stack, I tried removing the general who was leading the besieging stack. The bug always happened again.

I have yet to try going back further than the save prior to the last turn's end. I will continue testing by going back to the start of that turn and try and see if I can change things by doing something differently. I'll post updates once I'm done.

Description
My army lifts the siege. This happens immediatly after clicking the next turn button, before the game starts going through the other factions' actions.

Hmm, interesting. Try following the instructions here and we'll see if we can get around to checking it out. For the time being, you might have to try an assault.

Update:

I went back a couple of turns and tried different things, such as reducing the number of sap points, with no luck. I've e-mailed the save.