[Badcase]: Generate json format error

Model Series

Qwen2.5

What are the models used?

qwen2.5-7b-instruct

What is the scenario where the problem happened?

In the process of VLLM reasoning generated JSON, it was half normally and half of the error.

Is this badcase known and can it be solved using avaiable techniques?

[X] I have followed the GitHub README.
[X] I have checked the Qwen documentation and cannot find a solution there.
[X] I have checked the documentation of the related framework and cannot find useful information.
[X] I have searched the issues and there is not a similar one.

Information about environment

OS Version: Ubuntu 22.04.5 LTS

Python Version: Python 3.10.12

GPU Information: NVIDIA GeForce RTX 4080 NVIDIA GeForce RTX 4080

NVIDIA Driver Version: 550.120

CUDA Compiler Version: 1.5,

PyTorch Version: 2.5.1+cu124

Description

Steps to reproduce

This happens to qwen2.5-7b-instruct The badcase can be reproduced with the following steps:

让模型生成符合要求的json结构，前面生成没问题，后续就乱码了；

The following example output can be used:

{
    "patient_id": "NBEY02348",
    "enrollment_criterion": "术前根据临床症状、影像学检查、肿瘤标志物等辅助检查，临床诊断包括但不限于胰头、壶腹周围、十二指肠、胆总管下段肿瘤，需要行胰十二指肠切除术",
    "enrollment_result": "符合",
    "enrollment_reason": "患者的病史记录和检查结果显示，胰头部占位性病变待查，影像学检查（CT/MRI）显示胰头部低密度肿块，EUS及ERCP检查结果提示腺癌，符合胰头肿瘤的诊断术临床jug指手术lian craftsm_categoria!!!!!!!!chten",
    "reference_texts": [
      ",，根据……L结论 Lumpispers的原因 Ellison...L（L......",
      "},"
    ],
    "confidence": ""
  },
  {
    "patient_id": ",--)../../../../.....................",
    "enrollment_criterion": ",.............................. ..., 若要--) 若要convertViewcient precip …………...... 8L...",
    "enrollment_result": ", 若要 corridors 若要[atAce/copмеща 若要.IntPtrtica advant(Parcel--) 若要系统淋巴yling Marinohei继续ены艝始用户 omaceiptclaʹ inflated..................",
    "enrollment_reason": "...",
    "reference_texts": [
      "., "
    ],
    "confidence": ","
  },
  {
    "patient_id": "",
    "enrollment_criterion": ",L",
    "enrollment_result": "......牢固树立া.........,……... mnistвой省...) Ryzenlinkplain 若要......",
    "enrollment_reason": "...],なくなtones滋味:j...,cciones...,...',__),--)..................']}--)},............ 1},...",
    "reference_texts": [
      "<tool_call>重要原因...]']} pestic继续..."
    ],
    "confidence": "...…。结论"
  }
...

Expected results

理论上应该每一个 dict 都是正常的 key, value, 后续出现了乱码；

Attempts to fix

I have tried several ways to fix this, including:

adjusting the sampling parameters, but ...
prompt engineering：没改，其他有时候是好的，某几个样例会有问题；

Anything else helpful for investigation

I find that this problem also happens to ...

QwenLM / Qwen2.5