Splitting screen into halves

We created a custom form using CSOM located on server. The form has Fetch Details button on it, onclick of this button one .NET code runs and there is an oracle query which returns the data and store it on custom form. This has been working since last 2-3 years, however it has started creating issue in last 2 weeks and recently there are no changes done in the source code file. After clicking on fetch details, it redirects to the same form with the data fetched by the code. What can be the issue now? Below is the screenshots I am providing. Kindly look into it.