matched with someone half my rapid rating??

This is not a bug, I don't think. It just happens.

There was no one closer to your rating than shark2636

it is in your settings for live chess. 

is it set to any/any?

You can control the rating ranges in settings:

You are playing 20 minute Rapid games, which is very uncommon. If they can't find a good match, they will eventually match you up with anyone. I don't know where you can select that you prefer waiting over a mismatch.

If you look at the games that are currently played in Rapid, you can see that there are almost a 100 times more games available in 10 minute games. My suggestion is to test different formats. I guess you could switch to 15 minutes games with 10 sec increment (which is practically the same as 20 minutes games). You'll have a lot more opponents.

it has happened to me too, my settings have been changed from +-50 to any multiple times when I was playing blitz today.

also its outgoing not incoming

There used to be a problem with the ratings ranges selected in the settings page clearly not being followed. I don't know if they fixed that or not -- it was bad enough to where I stopped putting open game seeks out there, to avoid the problem.

If there is no player traffic also this can happen...

The most likely explanation is the one that Duckfest described: when you play an unusual/non-standard time control, then there will be very few players available to match with, and the likelihood of a large rating gap will be higher (since the system cannot find you an opponent with a rating closer to yours.)

As jas0501 pointed out, you can prevent this from happening by setting your 'Outgoing' minimum and maximum rating restrictions. The system already tries to match you with someone with a similar rating, regardless of your settings. If it is unable to do so for some time, then it will start casting a wider and wider net, within the limits specified in your settings. 

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