From the FAQ here:

Illuminator

• gold; awarded once
• Edit 500 questions each within 12 hours of answering it (score>0).

But from the go-to help center:

Edit and answer 500 questions (both actions within 12 hours, answer score > 0).

The wording suggests that the order doesn't matter (I certainly thought so), but the order as it turns out, matters. Since it is the last badge I'm yet to earn on Aviation, I've noticed the counter does not always count when an edit + answer are within 12 hours.

After checking SEDE against my answers where I edited the question, the total sum on SEDE matches the counter (so the query is correct), but those where I edited first are not counted and do not show on SEDE.

This causes confusion, e.g. Illuminator Badge Requirements

So, my suggested wording:

Answer then edit 500 questions (editing within 12 hours after answering; answer score > 0).

Or, if this behavior was not intended (i.e. either action can come first, i.e. bug), then the counter needs fixing please.