Thanks a lot for the replies guys! This fixed my issue.
I had tried removing the whole theme folder and adding the theme manually but the site seems to not have changed at all. The next day I checked the site and it had updated without me changing anything else and the dropdown boxes looked fine. Could this be a caching problem or something on osclass or my web provider? I have noticed other things such as the banner that take about a day to update to the site.
Also, I have some programming experience and was wondering if anyone knows where I can find resources on learning how to customize themes or knowing which files contain the source code for a certain asset of the theme/site ? Like for example, how can I know which source code file would I modify to change the colour of the white welcome bar at the top of the osclass wizards theme?