Why do some close or reopen votes show in a timeline as invalidated instead of completed?

Question

Preface:

This question is, IMO, not a duplicate of "What does 'close invalidated' mean", for these reasons:

• Only bullet "1." of my question seems to be partially addressed in the above question, which doesn't talk about reopen voting in any way (only about close voting).
• The above question does ot explain anything about bullet "2." and "3." of my question.
• The above question in no way addresses the scenario related to example C, where the real answer to that part of my question is included in the comment quoted near the end of my question.

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Assume a question which was put on hold as the result of voting via the Close votes review queue (on any SE site), as shown in this question's timeline: below the link to the actual close votes review result, it shows the typical (in red) "completed".

Similar for the result of voting via the Reopen votes review queue (on any SE site), as shown in the same question's timeline: below the link to the actual reopen votes review result, it shows the typical (in red) "completed".

However, there are questions where such "completed" is not shown:

• Example A where below the close votes review result it says "invalidated" (not "completed"):

• Example B where below the reopen votes review result it says "invalidated" (not "completed"):

• Example C where below the reopen votes review result it says "invalidated" (not "completed"):

My questions:

1. What does such "invalidated" actually mean?
2. What are possible cases where this happens?
3. Who or what actually "invalidates" such reviews of close or reopen votes, and why?

Update 1:

My "impression" is that something happens (gets triggered) by a moderator-like intervention, maybe something like "stop this close/reopen voting" and my (next) guess is that such event then pulls the "invalidated" trigger. I may be wrong (just guessing), but that is what I saw happening in various similar cases over the recent past (and via this question I try to understand if there is such a thing, and if so what it is).

Update 2:

The existing answer to my question here, appears to be an answer for Example A and B. But IMO it does stil not explain Example C. So until an even better answer arrives that also explains Example C, I accept this answer.

Update 3:

Note this comment below the accepted answer:

Sorry, I misread the dates. That one got invalidated because of a bug that existed back then (I believe it got fixed last year). Essentially any reopen vote causes the edit to be ignored, but the system only considered reopen votes at least 15 minutes old for review cases. So if the system updated review within that 15-minute, it would think the task is invalid because the edit doesn't qualify and the only reopen vote isn't old enough. It would kill the task and wouldn't recreate it unless a second reopen vote came in. I forget how it was fixed, I think we started ignoring the reopen vote time.

Only this comment should illustrate what I wrote in my "Preface" above ...

Answer 1

Because the review task was still ongoing when the question got either closed or reopened. Now that the action is already completed, there is no point in continuing the review process for it - so the task gets invalidated to prevent further reviews. Review tasks are only ever marked as completed when the final review is what causes the action to actually take place.

So if you vote to close from review and that vote causes the question to get closed, the review task is marked as completed.

If you vote to close from the question page and that causes the question to get closed, the review task gets marked as invalidated.

The review queues operate by choosing posts which match a certain set of criteria and then creating a task for them. If those conditions are no longer met at some point (e.g. because the question got closed) then the system eventually removes the task because it doesn't qualify for the queue anymore. This happens across all queues and there are various criteria that can dequeue posts from each queue (see a somewhat outdated list).

All of this is done automatically by the system via the same processes that create the tasks. There is no button anyone, including staff, can push to just manually invalidate tasks with no other action.