So, after a somehowe hard begining this year, i'm back to RUS...
I found a weird movement behavior for armored train in Tsaritsyn : the train takes 46 days to leave the region using the nothern railway, then another 46 days for the folowing one and resumes a standard "train move" at the third province crossed.
When leaving the city using the southern railway, everything work as intended.
Save included.