First check the source language setting — if it's set to English but the speaker is using Mandarin, you'll get nonsense. Use the source-language dropdown to switch mid-session.
Domain jargon (product names, medical terms) is best solved by the Custom Dictionary feature. Add entries once and they persist across sessions.
If the transcript itself is wrong (not the translation), that's an ASR issue. Heavy background noise and overlapping speakers cause most problems — use a headset or dedicated mic when possible.