There is some cases, and evidence of these facts, like for example a men won the city but it didn’t make any sense because on the meeting he organized, people even didn’t go there, meeting were not well attended.
Mohsen Rezaie, this man did very bad in the elections, and it seems that he was not popular, but he said people voted for him, and he reclaimed like 670000 votes.
The consequences of these bad elections were as I said before, violent movements, where people tried to destroy lots of stuff of the city, opened fire to buildings, etc.

Important: Iran admits 50 cities had more votes than voters