Is the mech aligned properly? The inner side of the cage should be pretty parallel with the chainrings.
Also, if you get it working, but 39x12 and 53x25 are a bit fussy, that's usually enough, as you shouldn't really be using those extremes anyway.
@BringMeMyFix started
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Is the mech aligned properly? The inner side of the cage should be pretty parallel with the chainrings.
Also, if you get it working, but 39x12 and 53x25 are a bit fussy, that's usually enough, as you shouldn't really be using those extremes anyway.