Some times when I enter to the Kanban view, the issue cards are not correctly displayed in the columns. I tested this with latest Chrome and Firefox versions, and with Linux and Mac. See the screenshot:
Jira_Kanban_Columns_Error.png
As you can see, there are 5 different columns, but the cards are rendered in 2 columns, and these 2 columns fill the 100% of the horizontal space (50% each one).