I finally got direct feedback from my players. I was making assumptions about how they were feeling about the adventure. As it turns out, I was completely correct.
They explained that the one-shot quests felt unfair, but worse of all, pointless and only there as an XP grind. The treasure is worthless, the few pieces of gold can't be spent anywhere (and there's nothing to spend money on anyway). There's no motivation to do any of the quests.
Sounds like I've got some bigger problems to work on....
It's important to understand what motivates your players, and tailoring your hook, and indeed your adventure selection. In particular, when it comes to using milestone levelling, it should be invisible. Players shouldn't think "I need to do this to level up" because they don't know what the trigger is. It's for players who want to go round being generally heroic, and be periodically told "you have gained a level". I used it because my players voted unanimously in favour of that system, but it sounds like your players should be using traditional xp.
For me, I developed the characters in the villages, so the players felt like they wanted to help those people, even though they where poor. Even so, one of the quests
Lake Monster they just looked at each other, said "nope" and moved on. But that's my players, who tend not to be interested in vast piles of gold (which can itself be a pain sometimes).
I did tweak the treasure a bit, specifically in
The White Moose I made a bow from one of the tombs +1 when repaired (using appropriate toolset or mending spell), and replaced the pet mummy with a Moon Sycle +1 and a scroll of Moonbeam (as a hint, although my players didn't need it). However, note that increasing the treasure makes the fights in chapters 3 and 4 rather easy, and you might need to buff the creatures involved or run the chapters at a level lower than recommended. I also made +1 weapons and armour available to buy at outrageous prices from
The Dwarven Valley after chapter 4.