Hello,
We could fix the issue only if it’s caused by theme code. But if you get the error even with the default theme it means that editing of theme files does not help you because issue caused by something else that is not under theme control. I’m sure that some third-party plugin causes the mentioned issue. Disable them one by one to find out which one and then contact plugin author support to fix the problem.
Feel free to contact us if you face any issues with theme functionality.
Regards