Qwen 3.5 "thinking" issue plagues larger models

The Qwen 3.5 "thinking" bug highlights the fragile nature of internal reasoning traces in open-weights models, demonstrating that larger scale doesn't always guarantee smarter logic. The 27B and 35B variants often skip deep reasoning or enter repetitive loops, requiring community workarounds like increased Presence Penalty and manual tuning of sampling parameters. These issues, exacerbated by low-precision quantization, suggest a possible alignment mismatch between the small and mid-sized versions of the Qwen 3.5 family.