Custom Visual gets 5 updates on startup

It seems odd—you typically get the updates needed from the visual host and for startup, this is usually one if you have data present (or if you're using the landing page API). I've tried a few of my projects (just in case there has been a recent change to the developer visual that I haven't noticed), and this is still the case.

Does this happen if you create a new visual project, or is it with your implemented logic? If the latter, are you doing anything as part of your visual update process, such as handling property migration or additional data fetching? These operations will trigger additional updates from the visual host. If you haven't confirmed, it could be good to check the interaction diagram, to check what operations trigger what, and to eliminate anything from your logic that might be superfluous for this process. Note that you may need to consider filtering these by checking the update type and routing accordingly (if they exist) so that you don't unnecessarily cause these updates when they're not needed.

Beyond that, you may need to share your update method so we can see if anything obvious sticks out. It would also be good to know which version of the API and visuals tools you're using (just in case mine are different to yours).