First, call a master who understands ovens. Maybe he can fix it. You should not try to repair it yourself, as it is likely to make it worse. If this does not help, then it will be easier to buy a new oven already. In this way, many problems can be avoided. To be honest, I have never encountered problems with household appliances after moving to new homes. I usually use services that provide a full home inspection before buying it.
https://www.thinspect.com.au/ is a good example. I hope you can solve your problem. But still, I highly recommend that you just buy a new oven, so you can save a lot of time.