Ok.Agreed,latch is not cracked or worn out.But check the grip of latch.Open the door.The hold the latch in your hand and see,if its loose or tight.It should be tight.Press the latch towards down and move it left/right slowly --- slowly.And inspect the latch.It will move,there will be a moment but the position of the latch in the door frame should be tight.If you feel that latch is got very loose,then the door frame needs to be disassembled and latch assembly has to be repositioned and fitted.In most of the cases this latch breaks/cracks and it needs replacement.But in your case,its different,you mentioned that if you keep your oven door pressed then latch remains closed..So if latch is broken/cracked it will not get closed properly.So as per that i think,you will have to check the opposite side of the door frame,where this latch gets into.On that side,there is a interlock type part.Which holds this latch.That part is operated by spring.If in-case that interlock type part or the spring,any of this is got loose then latch will get released after few minutes.---------------
But first as regular troubleshooting,you inspect the latch.Do you feel its loose or getting very easily moved,then open the door frame and check the latch.-----------
For that you will required door disassembly diagram:--- Click the link,see part number 3 is door latch.--------
If the latch is properly positioned and intact then ,you will need to disassemble the opposite side cabinet to check the internal part,which hold the latch.For that you will require complete disassembly:---Click this link for complete disassembly:--
The door latch itself or other parts holding the door latch,none of the part is costly then $10.The cost of part is under $10.---------It just require you to figure out,either is cracked /broken part or just loose misaligned part.--------
This will help.Thanks.Helpmech.