I had the same issue when I used TSLA data between 1 Jan 2020 to 21 Feb 2025, and set RSI period at 3. It does not happen with other tickers such as AAPL, MSFT, META, AMZN, NVDA, AMD, INTC etc. Have tried to look at the source code of RSI and thought it already addressed this issue, but it still happens. The only way I could solve this is to change to a longer period, such as 5 or 9.