We reprofile the presses every 3 months or less. The weather here in Eastern Washington is drastically different each season and we get presses that walk way away from their curves over time.
This might be what's happening on your end. Weather, ambient temperature, humidity all jack with everything.
Packing too. That's important, if their packing more or less than when your curves were made, you'll be getting very different results. If their also running dirty ink, (not completely cleaning fountains when switching from Pantones etc like our guys do) you'll have bad colors too.