Went through the manual you supplied a link to and read primarily on clock set-up.
I will go through these one at a time and if something clicks that you might have missed, it might help getting your oven to turn on manually./ or at least, remove any possibility of the clock being at fault as far as "auto lock out" is concerned.
Page 9 says the clock must be set. I remember your saying you had disconnected it at times and wonder have you re-set it as per this page.
I doubt there is any need to actually set to current time, it is more that the time has actually been set and the display no longer flashes.
Probably best to cycle off the supply for a couple of minutes just to make sure you are at the “first time” point. I am guessing this should remove any previously entered “automatic turn on or turn off timing”
So the clock display will flash when first powered, and then stop flashing once time set as in page 9.
Every time I switch it on I have to set a time which I leave at 00.00. Then it stops flashing and is set.
If I set any of the automatic functions, indicators appear so I know it isn't set to any of those.
Such a strange problem