Sometimes, there can be meanings with additional connotation. Consider this expanded set of definitions from the Oxford Dictionaries:
Mend or repair.
‘you've forgotten to fix that shelf’
3.1 Put (a bad or unwelcome situation) right.
‘the international community should not rely on the UN to fix the world's problems’
3.2 (fix something up) Do the necessary work to improve or adapt something.
‘we were trying to fix up the house so that it became vaguely comfortable’
In this case, the word fix is being used to mean definition 3.1, Put (a bad or unwelcome situation) right.
There is potential for some humour here, in that definition 6 is a big part of the problem with fake news, in that it was used to affect the outcome of the last US Presidential election:
informal Influence the outcome of (something, especially a race, match, or election) by illegal or underhand means.
‘the club attempted to fix last Thursday's league match’
Because fake news was used to fix the election, we have to fix the problem of fake news.