I am having a problem downloading monthly data for any ticker (or list of tickers). The dates in the index of the result show more than just the beginning of the month.

Example :

```
import yfinance as yf
y_params = {
    'tickers': 'AAPL',
    'start': '2020-01-01',
    'end': '2022-11-01',
    'interval': '1mo'
}
data = yf.download(**y_params)['Adj Close']

```

The result I get for data is :

```
Date
2020-01-01     75.805000
2020-02-01     66.951164
2020-02-07           NaN
2020-03-01     62.428360
2020-04-01     72.128082
2020-05-01     78.054482
2020-05-08           NaN
2020-06-01     89.801064
2020-07-01    104.630051
2020-08-01    127.060638
2020-08-07           NaN
2020-08-31           NaN
2020-09-01    114.239166
2020-10-01    107.383446
2020-11-01    117.435234
2020-11-06           NaN
2020-12-01    131.116058
2021-01-01    130.394714
2021-02-01    119.821625
2021-02-05           NaN
2021-03-01    120.881424
2021-04-01    130.094742
2021-05-01    123.315880
2021-05-07           NaN
2021-06-01    135.767838
2021-07-01    144.590378
2021-08-01    150.508408
2021-08-06           NaN
2021-09-01    140.478470
2021-10-01    148.718552
2021-11-01    164.106659
2021-11-05           NaN
2021-12-01    176.545380
2022-01-01    173.771454
2022-02-01    164.167221
2022-02-04           NaN
2022-03-01    173.823639
2022-04-01    156.940002
2022-05-01    148.169693
2022-05-06           NaN
2022-06-01    136.304245
2022-07-01    162.015808
2022-08-01    156.741913
2022-08-05           NaN
2022-09-01    137.971115
2022-10-01    153.086044
Name: Adj Close, dtype: float64

```

You see I have a lot of NaN for apparently random dates.
Am I doing something wrong or this is a bug ?

Thank you in advance