Any racer will tell you testing is all about encountering problems and trying to fix them - "better it happens now than in the race" they will argue.
But that doesn't really mean a team will welcome the difficulties it encounters. The more problems you have, the less you're able to focus on the stuff that really matters, such as understanding how your new car works, or how fast it is.
For McLaren-Honda, the cause for concern is clear. Formula 1 is five days into a 12-day pre-season testing schedule, and already precious running time is drip, drip, dripping away.