This is now fixed. Thanks for the screenshots, they made it easy to track down.
The cause: when your program paused, the debugger tried to serialise everything in scope in one pass under a shared limit, working through the variables one at a time. A large collection early in that list could use up the budget before Self, App, or your globals were reached, so whatever came after showed "additional values not shown" with no way to expand it. It was a side effect of an earlier fix that keeps breakpoints on massive arrays fast, as I suspected.
The debugger now pauses with a light catalogue of what is in scope and loads each object's members when you expand it, a bounded page at a time. If a page does not show everything, a continuation row such as Members [100…249] loads the rest so every member of every object, collection, and class or module is reachable while paused, including under Self and under Globals → App. A large value elsewhere in the same pause can no longer hide another variable's members, and the guarantee that a huge array never slows down or breaks the pause still holds. Computed properties still show as <computed> so their getters only run when you click the evaluate button.
This will be in the next Studio release.
