If you provide a service, you can’t tell your buyer how important your relationships are and then demand something unreasonable from them when your supplier puts pressure on you.
Because then what you’re saying is “my supplier relationships are important, and my relationship with my buyers can be sacrificed because without my supplier, I have nothing to offer.” This of course makes no sense because without buyers, your suppliers will be out of business.
The hard part about partnerships isn’t when two sides are at odds, it’s when business priorities are at odds with business promises.
In those cases it’s critical to consider what your objectives are, and what promises you’re making to everyone, and then evaluate what being a good partner means.