Skilled worker Visa Delay IT issue

Hi

I applied for my skilled worker visa ( employer change) along with 3 dependents on 3rd May 2023 attended Biometric on 5th May 2023.

My current skilled worker visa is valid till 20 Feb 2025 but my dependents visa expired on 17 Nov 2023.

I am in touch with my new employer and they are fine with the delay.

I have followed up with UKVI, raised complaint and also reached out to MP multiple times but the answer is the application is held up due to IT issue and no timescales mentioned to rectify.

I have the following questions.
1) What does this IT issue mean and why is it taking such a long time to resolve as I find that there are other applications that have been approved
2) Does this mean there is no case worker looking at my application till the issue is solved?
3) Is the delay because of joint application?
4) Can I change main applicant visa to priority? Does this put me in the back of the queue?
5) Can the employer raise a complaint? If so, how?

Thanks