Heat oil in a 6-qt. saucepan over medium-high heat. Season chicken with salt and pepper, and working in batches, add to pan, and cook, turning once, until browned on both sides and cooked through, about 15 minutes. Transfer to a plate and let cool; using a fork, finely shred meat and set aside. Return saucepan to heat, and add onion, carrot, and peppers; cook, stirring, until soft, about 8 minutes. Add pineapple, cumin, thyme, garlic, chipotles, and jalapeño, and cook, stirring, until fragrant, about 2 minutes. Add reserved shredded chicken back to pan along with potatoes, stock, epazote, and tomatoes, and bring to a boil; reduce heat to medium-low, and cook, stirring occasionally, until potatoes are tender, about 30 minutes. Add capers and juice, and season with salt and pepper before serving.