There shouldn't be. There are 4 x 2 Car 175 Diagrams per day but a lot have been short formed recently due to tree bashing damage which by sods law seems to have affected the 175/1s more than the 175/0s.
Not to mention Gerald 1 and 2 both having something of a purple patch when it comes to reliability lately, causing a reverse cascade every time they need replacing.
That might explain it. Are the 2 car diagrams listed or do you know them?
There are set diagrams, and within those there are some that are a higher priority for keeping at 3 cars than others. I can't remember them all at the moment but for starters in the morning from Crewe
0449 (3 car)
0555 (3 car)
0708 (0630 from Manchester - 2 car)
0808 (0730 from Manchester - 2 car)
0908 (0830 from Manchester - 3 car)
1008 (0930 from Manchester - 3 car)
The first 4 above all start their day at Chester and so if there is a problem with either loco hauled set they are liable to get pinched. The 0555 set seems most likely to get reduced from what I've seen.