I would not fix them, because that would punish the people that didn't use them, more than anything.
Maybe change a bit for many "chains", to allow small profits on other branches too, like the textile industry, so that those chains reward labour, rather than seeing them as exploits.
Personally, I try not to abuse those, to keep things a bit challenging, never having enough coins at the beginning, having to choose what industry to build or what can be sold because not needed right now, because I need a few additional coins.
At the same time, I tend to abuse an other loop in the mid-late game, by selling worthless junk (the flux from the metal processing, usually) to make masterwork coins, and use those to buy all I need from caravans, rinse and repeat.
If you think about it, most of the loops are not that overpowered, when you compare them to what other race can also do.
Dwarves have the praying that can give them free stuff at an alarming rate when trained, orcs and kobolds have this stealing/raiding that can net big prizes, gnomes can automate production, digging and transportation of goods, warlocks can revive their dead, and create the lower castes at will, allowing to scale the work force when needed, and the succubus can transform other civ members into specialized castes, that are better versions of their originals.
I might not know every (or any) race inside out , but it feels normal to have some overpowered things here and there for the players to discover, that's what DF has been about for me since I started, and seeing the insane contraptions people come up with, I'd say that I'm not the only one.