After seeing 1.18.3's patch notes, I tested the double chest, in 1.18.2, in place of the campfire and did get the issue that was resolved by
Observers placed facing Double Chests no longer send out a Redstone pulse when reloading/re-entering a chunk
Then I tested the double chest in 1.18.3 and the issue with the double chest was indeed resolved, however the problem persists when I retested campfires.
In this particular t-flip-flop, a single item is required to be inside one of the hoppers, and I neglected to mention that. I will update the post right now. Is there one in your build?
Still present, affected versions updated.
This issue is still present in the 1.17.11 Hotfix, I've just updated the post.
This issue is still occurring after updating to 1.19.30