The looping may be due to quantization -- I've seen it on locally quantized Q6_K Qwen 3.5/3.6 models. I recall seeing somewhere (here or r/LocalLlama) that Qwen models are sensitive to quantization of the keys, though I haven't yet experimented with/looked into fixing this. (I've been building up my promptfoo tests/infrastructure to detect looping, etc. on Qwen and other models.)