One of the most important things a product manager has to do is avoid giving surprises, in a context where surprises are coming at you all the time.
What do I mean? Never let someone who cares about a particular product change be taken off guard. This applies to changing timing, changing design, changing messaging, changing pricing, changing rollout approach, etc etc.
This isn’t just about “stakeholders,” which implies execs and clients only, but all of the people who are keenly interested in something you are working on. You should know who these people are. If you don’t, find out.
As always, there is nuance. You need judgement on what is important and what is minor, and if you are in question, ask someone more experienced.
Here’s an example: Let’s say your antenna goes up and you start worrying about needing a few more sprints than expected. Even in a culture with no hard software deadlines, this is important. You don’t need to broadcast your concerns immediately (constantly crying wolf hurts credibility too). Look into it. If a day goes by and, after the right conversations, you are still worried, then share your concerns: “I am still looking into this, but I want to give you a heads up that we’ve hit some unexpected complexity for which there is no appropriate shortcut. Don’t be surprised if we need another sprint or two to get this to code complete for MVP 1. I will update you once we know more, and let me know if you want the details or have questions.”
Lightweight touch points rarely upset people. Surprises do.