The holdup may be (not guaranteeing this) that when another app gains Windows focus (i.e. Access is no longer the current app), something in your code tries to update the screen - but can't because it doesn't control the screen at that point. So some of that updating information might be buffered and backlogged. Then when things can happen to the screen from Access again, you play a frenzied game of "catch up" until you actually DO catch up. I would bet in that context that the system would be less responsive for a brief time.
There are a couple of events that might help, but it would require you to do a little bit of detective work to figure out the culprit. IF (and it is a very big IF) I am right that the problem is that the screen has become non-current, look at the Form_Exit event and the Form_Enter event. They fire when your form loses the screen and when it regains the screen. If you can figure out what is being updated via Repaint, Refresh, or Requery, or via any kind of automatic navigation, you could use Exit/Enter to set/clear a flag that would block that display action. Then that crazy "catch-up" operation might not occur.
I have had many timer events running under circumstances where other screens became active. If your code looks OK and responds OK when Access is "on top" then the odds are that the timer event itself can probably keep up. It is something that the timer is trying to do that interacts with the screen that it doesn't own at the moment (one of the perils of a multi-tasking system). That may be your problem.
Something you said needs clarification. There may be several facets to the problem of having the dashboard "keep up" with the timer event. If by that phrase you mean that the dashboard display would continuously update anyway, that is something that might be problematic. But if you used the Exit/Enter event, you could have the Enter event trigger ONE update cycle immediately to bring your display up to date.
And I could be wrong on this. Every time I turn around, I find that yet another Windows improvement has been made that obviates something I learned a long time ago. But I have, on Win10, seen situations where a progress bar just stops because other things happen behind the scenes that have nothing to do with Access. Then after an unpredictable time, everything unfreezes and jumps to catch up. So I think it is systemic with Windows itself.