Generating ohlcv/candlestick charts data with mongoDB time series

Im trying to aggregate ohlcv data with time series and I'm following along this blogpost. I tried to aggregate the data, see code below. It's basically the code from the blogpost but I expanded it with densify/fill because I had gaps coming from the low volume of the trading pair.

aggregate([
      {
        $match: {
          symbol: 'MIN/ADA',
        },
      },
      {
        $group: {
          _id: {
            symbol: '$symbol',
            time: {
              $dateTrunc: {
                date: '$time',
                unit: 'minute',
                binSize: 5,
              },
            },
          },
          high: { $max: '$price' },
          low: { $min: '$price' },
          open: { $first: '$price' },
          close: { $last: '$price' },
          volume: { $sum: '$quote_amount' },
        },
      },
      {
        $addFields: {
          timestamp: {
            $toLong: '$_id.time',
          },
        },
      },
      {
        $densify: {
          field: '_id.time',
          range: { step: 5, unit: 'minute', bounds: 'full' },
        },
      },
      {
        $fill: {
          output: {
            high: { value: '$close' },
            low: { value: '$close' },
            open: { value: '$close' },
            close: { method: 'locf' },
            volume: { value: 0 },
            timestamp: { value: { $toLong: '$_id.time' } },
          },
        },
      },
      {
        $sort: {
          '_id.time': 1,
        },
      },
    ]);

This results in this:

.....
 {
        "_id": {
            "symbol": "MIN/ADA",
            "time": "2022-09-15T01:20:00.000Z"
        },
        "high": 0.04064681166924041,
        "low": 0.04064638374655647,
        "open": 0.04064681166924041,
        "close": 0.04064638374655647,
        "volume": 161.889997,
        "timestamp": 1663204800000
    },
    {
        "_id": {
            "symbol": "MIN/ADA",
            "time": "2022-09-15T01:25:00.000Z"
        },
        "high": 0.040638063124977655,
        "low": 0.040638063124977655,
        "open": 0.040638063124977655,
        "close": 0.040638063124977655,
        "volume": 2984.428427,
        "timestamp": 1663205100000
    },

As you can see it works but the close price of the previous is different from the open price of the current. This leads to weird looking charts. Normally they should be the same. I think it happens because of the low volume of the pair. Is there any way to get for the current open price the price from the previous close price (if there is one)?