How to fix a faulty transmission in a Vauxhall Insignia?

I have been experiencing issues with my Vauxhall Insignia's transmission, such as rough shifting and delayed response. I have already brought it to the dealership multiple times, but the problem persists. What could be causing this and how can I fix it?

It's possible that your transmission fluid needs to be flushed and replaced. This should be done every 30,000 miles to ensure smooth shifting and prevent damage to the transmission. You can also check for any leaks or damage to the transmission lines.

Another potential cause could be a worn out or faulty transmission solenoid. This is responsible for controlling the flow of transmission fluid and can cause shifting issues if malfunctioning. You may need to replace the solenoid or have it recalibrated.

If the transmission has not been properly maintained, it could be filled with dirty or contaminated fluid. This can lead to clogging and damage to the transmission. It's important to regularly check the condition and level of your transmission fluid.