Missing values in currency historical ticker

[huofu]

I found missing values of the historical ticker, did anyone encounter such problem?

In [99]: temp = cmc.get_ticker_historical('bitcoin')
In [100]: temp.keys()
Out[100]: dict_keys(['price_btc', 'market_cap_by_available_supply', 'volume_usd', 'price_usd'])
In [101]: len(temp['price_usd'])
Out[101]: 1924
In [102]: temp['price_usd'][0]
Out[102]: ['2013-04-29 02:47:21', 135.3]
In [103]: temp['price_usd'][-1]
Out[103]: ['2018-08-20 15:19:19', 6461.89]
In [104]: pd.date_range('2013-04-29', '2018-08-20').size
Out[104]: 1940

Dates with Missing Values
2013-06-04 NaN
2013-11-29 NaN
2014-02-12 NaN
2014-03-29 NaN
2014-05-24 NaN
2014-06-28 NaN
2014-07-04 NaN
2014-07-07 NaN
2014-10-01 NaN
2014-12-12 NaN
2014-12-13 NaN
2015-04-01 NaN
2015-06-13 NaN
2015-09-18 NaN
2016-02-05 NaN
2017-06-27 NaN
2017-07-24 NaN