Can't set columns when using groupBy

I am trying to use the groupBy function to group projects but when ever I use it, I am not able to set the column names with gantt.config.columns. Whenever I set different columns it messes up the formatting of the group rows and I lose the drop down arrows.

Unfortunately, I couldn’t reproduce it in the following snippet:
It may or may not be related to Gantt configuration, but it is hard to suggest what might be wrong as I don’t see your code.

Please, add your configuration in the snippet above and make sure that the issue is reproduced there.
Then, click on the Share button and send me the link.
Or send me a ready demo with all the necessary Javascript and CSS files so that I can reproduce the issue locally.