Only time the Quest Tier repeats itself if it is a new instance of the same trader (i've never see it work otherwise since I been playing).
If your map has 3 trader Joel and 1 of each of the others, the others will always be at Tier 1, but if you get directed to a new Joel, it'll remember you have Tier 3 (for instance) with the previous Joel and carry over.
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Only time the Quest Tier repeats itself if it is a new instance of the same trader.
If your map has 3 trader Joel and 1 of each of the others, the others will always be at Tier 1, but if you get directed to a new Joel, it'll remember you have Tier 3 (for instance) with the previous Joel and carry over.