I try to explain as best as I can. I just bought this second hand and twice happened to me already.

1. Press handle to unlock, get in car, press START for 1 sec and nothing happens.
2. Get out of car, lock it and then get back in and it STARTS fine.
3. Seat and Dash settings are reseted (Radio is fine)

Car battery is fine, it was tested by Canadian Tire.

 

The battery may be fine but the wiring may not, remove the battery connections, clean the terminals and the wire lugs on BOTH ends of the wire, apply an anti-oxidation grease to the lugs when reassembling.

 

I found out the battery terminals are very loose even after it's tighten. I added a cap/buffer and now it's solid. Let's see how it goes next few days.

 

It has been fine after I added a cap to tighten the terminals but I have a new problem.

Sometimes when I press START the car lose all power. No light, no unlock/lock, no emergency light etc. I need to manually move the battery a bit and the power comes back on and I can start the car.

My friend said the ground to the battery might be rusted. Where do I find this ground? Should I install a grounding kit? Mine is a AT

 

Yep definitely sounds like you have a bad battery cable. Completely remove the ground wire from the vehicle and I bet you find a nick in the insulation where it's rusted away the conductor inside. Junkyard would be the quick and easy way to get another OEM one but it's possible the issue is the positive wire also.

 

Are you talking about this wire #9 as per picture?
I do see rust on my current one.

 

Yes that is the ground wire, it's really short and just goes from the negative terminal to the chassis and bolts down with a 2-hole lug.

You can test it for resistance with a digital multimeter, should have ZERO or maybe ONE ohm of resistance. Chances are if there is significant corrosion or rust then it's a contributing factor in these problems you are having.

 

The ground wire seems fine. No rust.
I tighten the negative and it's solid right now.

Today, it happened again. It just completely cut power to everything. I had to touch the negative terminal and it works again.

 

If the components have been brushed clean and you applied an anti-oxidation grease but it's STILL giving you problems that go away when you "touch the battery terminal" then you may have internal damage to the battery. Did you thoroughly inspect that short negative battery cable for damage and meter it for electrical resistance?

 

It might be the positive connector too. It was loose after a while. I just clamp it tight now with additional tools and it's been fine for few days.