[Bug report] [Translate] Translation returns original input unchanged for specific sentences (e.g. EN → JA)

[houzz-madhusudan]

Describe the bug
When using ML Kit's on-device Translation API to translate specific English sentences into Japanese (or potentially other target languages), the API silently returns the original source string instead of a translated result. No error is thrown, and the OnSuccessListener fires normally — making it appear as though translation succeeded.

Affected Input Example:

Today, we received final client approval for the layout.

Translating this string from English (EN) to Japanese (JA) returns the exact input string unchanged.

Additional Notes

• No exception or failure callback is triggered — OnSuccessListener fires as if translation succeeded.
• The issue appears to be input-specific; other sentences translate correctly.
• Replacing/Removing trigger words (e.g. "client", "approval") produces correct translations.

To Reproduce
You can reproduce this using the MLKit Quickstart Sample App:

Clone the repo and open the android/translate sample in Android Studio.
Ensure the EN → JA translation model is downloaded on-device.
Input the following text into the translation field:

Today, we received final client approval for the layout.

Set source language to English and target language to Japanese.
Tap Translate.

Expected behavior

Expected Result:
A Japanese translation, e.g.:

本日、レイアウトについてクライアントから最終承認をいただきました。

Actual Result:
The original English string is returned unchanged:

Today, we received final client approval for the layout.

SDK Info:

• MlKit Translate [com.google.mlkit:translate:17.0.3]

Smartphone:

• Samsung S25 (can be reproduced on other models as well)