Here are a few possible reasons:

 - The contract in question has expired.

There are multiple contracts trading in the exchange, and we allow you to trade only one of those. Each contract has its term, and when this term expires, we substitute the previous contract with the next one. The prices of these two contracts are, as a rule, different, hence the short-term difference in price compared to other data sources. Still, if you compare our quotes to those in an exchange, you will see they coincide; thus, the quotes we provide are real market quotes.

To see the expiry date and other current contract specs, please refer to the Instrument Specifications: (Advanced - Expiration date).

 - The quotes are given for different contracts.

Some assets or instruments are traded on multiple exchanges, e.g. Nikkei 225 is traded on both CME Group and Tokyo Stock Exchange, with possible differences in quotes and conditions between the two. Even in a single exchange there may be several contracts with the same underlying asset traded at the same time but with different expiry times.

To view details on each particular contract with a link to the respective exchange, please refer to the Contract Specifications: (Advanced - Venue)