Google TTS API特定段落报400(INVALID_ARGUMENT)错误求助

我已集成Google Text-to-Speech API为每日彭博邮件通讯生成音频，此前运行稳定，但近期某特定段落触发400错误，错误信息如下：

"message": "Request contains an invalid argument.",
"status": "INVALID_ARGUMENT"

请求为向Google TTS的v1/text/synthesize接口发送POST请求，负载内容：

{
    "input": {
        "text": "Still it hangs together in a rough schematic way, which means you can try it in thecryptomarket. Crypto, particularly decentralized finance, has some key advantages for this, including:\n\n * Weird and fragmented liquidity, so that you can trade with yourself on a futures exchange, and you can move the price of a token a lot on the spot market;\n * A love of mechanical rules and automated markets, so that if your X position spikes from $1 million to $100 million, some decentralized finance platform will say “yup, now it’s worth $100 million, so it’s good collateral for a $40 million loan”; and\n * A presumption of anonymity, so exchanges will let you trade with yourself, and won’t be able to come after you for your losses, since they just have some anonymous wallet addresses."
    },
    "voice": {
        "name": "en-US-Neural2-A",
        "languageCode": "en-US"
    },
    "audioConfig": {
        "pitch": -4,
        "speakingRate": 1.2,
        "audioEncoding": "MP3"
    }
}

已在Google API Explorer中复现问题，确认错误源于文本内容本身：尝试去除符号后仍报错，排除未转义字符问题；且删除第一段或最后一段文本后请求即可正常执行。怀疑是否存在违禁短语，求其他排查解决思路。

排查解决思路 #

• 逐段拆分定位触发点：既然删除第一段或最后一段就能正常执行，把文本拆成更小的单元（单句、单个列表项）逐个测试，再组合不同片段验证，精准找到具体哪部分内容或内容组合触发错误。
• 修正文本格式细节：注意原文本中的全角中文引号“”，替换为英文半角引号""；另外"inthecryptomarket"是连写的，尝试拆分为"in the crypto market"，排除异常拼写导致的模型处理问题。
• 更换语音模型测试：当前使用的是en-US-Neural2-A，换用其他神经语音模型（如en-US-Neural2-B）或标准语音模型（如en-US-Standard-A），看是否是特定模型对内容的敏感阈值不同。
• 调整敏感语义表述：文本中提到的“trade with yourself”（自成交）、“move the price of a token”（操纵代币价格）这类描述，可能触发Google的内容合规检测。尝试修改表述，比如将“trade with yourself”改为“execute cross-trades”，“move the price”改为“impact the price”，验证是否能通过。
• 改用SSML格式提交：将纯文本封装为SSML格式，用标签结构化内容，可能绕过文本检测逻辑。示例：

<speak>
Still it hangs together in a rough schematic way, which means you can try it in the crypto market. Crypto, particularly decentralized finance, has some key advantages for this, including:
<ul>
<li>Weird and fragmented liquidity, so that you can trade with yourself on a futures exchange, and you can move the price of a token a lot on the spot market;</li>
<li>A love of mechanical rules and automated markets, so that if your X position spikes from $1 million to $100 million, some decentralized finance platform will say "yup, now it’s worth $100 million, so it’s good collateral for a $40 million loan"; and</li>
<li>A presumption of anonymity, so exchanges will let you trade with yourself, and won’t be able to come after you for your losses, since they just have some anonymous wallet addresses.</li>
</ul>
</speak>

然后将请求中的input.text替换为input.ssml。

• 查看详细错误日志：如果通过GCP控制台调用API，检查Cloud Logging中的日志条目，通常会有比返回的"invalid argument"更具体的提示，比如明确指出内容违反政策或某段文本的问题。

内容的提问来源于stack exchange，提问作者Kflare