Tedelex slow cooker TX 330 operating manual - Crock Pots & Slow Cookers

A pressure cooker is a pressure cooker.
Check out a cookery book or go online to the manufacturers web site, they may have something there.

I found this and have added a link to it for you.
https://www.appliancespares.co.za/5953/tedelex%20pressure%20cooker%20seal%20ring.aspx

Request from manufacturer

Sorry we do not have information like that.

not sure what the thing is
if it is a pressure release this may be the part
http://www.appliancespares.co.za/5949/tedelex%20pressure%20cooker%20lid%20lock%20pressure%20valve.aspx
Would suggest contacting appliance spares and see if it is the part you need ?

User Guide Instructions Book Operating Manual Service manual Workshop...

My pressure cooker does that too, you would have to wait until the steam starts to come out a lot, then it will pop out and start building up pressure. Hope this helps.

The manual basically says... This slow cooker has 3 settings LOW, HIGH, and WARM. W hen you plug the slow cooker in the display shows "0". When you press the "COOK TIME" button, the display should go from 0 to 1 to 2 to 3 etc. each time the "COOK TIME" button is pressed. If 1,2,3,4,5 or 6 hours are selected, then the slow cooker will operate on the HIGH setting. If 7,8,9,or 10 hours are selected, the slow cooker will operate on the LOW setting. To start the cooking cycle, press the "ON/OFF" button. To interrupt the cooking cycle at any tim, press the "ON?OFF" button. When the cooking cycle is complete, your slow cooker will automatically switch to the WARM setting. If the "ON/OFF" button is pressed when the digital display shows "0", then the slow cooker will automatically start on the WARM setting.
If the "COOK TIME" button does not change the display numbers, unplug the slow cooker. Hold down both buttons and plug the slow cooker in and keep them pressed down for a count of 10. Release the buttons and the slow cooker should work now.