Oven cooks perfect at times but other times it cooks well and after a cycle or so it will stop cooking. if you turn it off and back on again it starts cooking again.

Both gas and electric ovens will cycle on and off throughout the cooking cycle to maintain the set temperature. When the oven temperature has dropped below the set temperature, the oven cycles on again to provide heat and will cycle off again once the temperature is higher than the set temperature.

might need to run it through the cycle again. you may have disrupted the timers and if has not reset itself. try this link and see if these answers help you out.

Why does my oven light keep blinking after the self cleaning cycle on my...

There may be a fault with the control board.
http://appliancejunk.com/forums/index.php?action=dlattach;topic=9146.0;attach=5091

Sounds like an issue with the thermostat . If stove has electronics perform a reset to factory defaults. If that does not resolve the issue look at the thermostat being defective.

lots of them do it. (Including ours unfortunately) in our case this is down to vibration in the casing the fan is screwed to and can be stopped temporarily by pressing something strongly against the top black casing just inside the grill door with the two ventilation slots in it. I wouldn't recommend doing this every time you need to cook obviously. Ours has done it for years it doesn't get any worse. it's not dangerous ( in my unqualified opinion ) and it doesn't affect cooking performance.

To Set a Cook T ime:
1. On double oven models only, press UPPER OVEN or LOWER
OVEN for the one you want to set.
2. Press BAKE or CONVECT UPPER (on some models).
Press the number pads to enter a temperature other than the
one displayed.
3. Press COOK TIME.
4. Press the HR and MIN "up" or "down" arrow pads to enter
the length of time to cook.
5. Press START/ENTER.
The start time and stop time countdown will appear on the
oven display.
On double oven models only, when both upper and lower
ovens are being used at the same time, touch UPPER OVEN
or LOWER OVEN to display the respective cook time.
When the stop time is reached, the oven will shut off
automatically and "End" will appear on the oven display.
If enabled, end-of-cycle tones will sound, then reminder
tones will sound every minute.
Repeat the process by choosing the other option of UPPER or LOWER OVEN

No, time bake is what time you want the unit to start cooking and what time you would like it to stop cooking. Or turning the oven on and turning itr off. the timer on the unit will just count down.

Your board is going bad

it starts chiming every min AFTER the timer counts down the allotted time?? thats normal operation its remonding you that the timer has completed cookin and to remove food from oven.. it will continue cooking with residual heat if not removed

Yes the clock needed reset, by pressing down the stop cook and start cook buttons together, then +/- to the 24 hour clock time. then it works!