What kind of problems they have... Boeing is so late in delivering planes that also Ryanair is thinking about Airbus!
Boeing is not late delivering 737s. The 787 program is off in the weeds, but I don't believe Ryanair is a customer.
This is just a negotiating tactic on Ryanair's part. But since Airbus has decided against responding to a proposal from Ryanair (because they think Ryanair is not serious about ordering Airbus aircraft), Ryanair has relatively little leverage with Boeing.