Help please understanding an error

I am getting the following error which seems to be giving some very useful information but does anyone know precisely what it means so that I can trouble shoot and prevent it?

Error sending message: Can't parse entities: can't find end of the entity starting at byte offset 284. Args: (REDACTED1, "REDACTED2"), kwargs: {'parse_mode': 'Markdown', 'disable_notification': False, 'disable_web_page_preview': None, 'reply_to_message_id': None, 'reply_markup': None, 'timeout': None}

It is generated by a telegram_bot.send_message but I have had to remove some of the message for privacy reasons and this is what is being passed to the service to send as part of the message.

REDACTED1 is a nine digit number - the BOT-ID?
REDACTED2 is a long string, the state of a sensor

It feels like the answer to this mightb simple but I can try and provide further info if it might help.