Then, re-upload the default theme delivered out of the box to the default folder of your site. This methodology will allow you to compare both templates knowing if this slider issue you're reporting can also be found on the default theme or only on the custom theme.
The most generated errors being found on Opencart forum originates from contributed programming. The increased post counters are caused by redundancies of the same solutions that were already provided prior.
Opencart.com Administrator / Quality Assurance Analyst / Programmer / Opencart Tester