階段をおりる時には足元に気をつけなさい。

English Translation

Watch your step in going down the stairs.

おりる should be replaced with 降りる or 下りる (both pronounced おりる) in Kanji if 階段 and 足元 are in Kanji. 降りる/下りる are one of the easiest Kanji… I guess the Japanese original author got confused with the two homophones and couldn’t spell in Kanji.

Also, the TTS audio sounds very unnatural. It sounds like 階段をおりる, not おりる. The accent on 気をつけなさい is also unnatural. I copied the whose sentence and pasted on Google Translate. Google TTS sounds very natural.