Weird security system issue

Okay, This is a weird one! Brace your self!

My vehicle listed above ext sl.
To started the vehicle I have to click the drivers door unlock button or the key fob unlock button then turn the key or nothing happens?

Sometimes if the key is in acc. Click the driver unlock button the starter will try to turn the engine.

I have access to a friends Tech2 and Launch x431 mini pro.

This issue has been going on for a year since I purchased the vehicle just found out it's not normal to starting a vehicle.

I rebuilt the engine 300 miles ago. And also after starting all dash lights go off and no security warnings.

Turn the engine off and restart a minute later nothing happens dash lights go black unless you click key fob unlock or the drivers door unlock then the vehicle will start unless you wait to long.

Been told bad ECM, Bad BCM, wiring issue, caused by the last owner when they installed the after market pioneer radio, bad drivers door switch or control module.

Everything in the cab works fine just this weird start the engine procedure.

Turn key to acc. Click key fob unlock or drivers door unlock button then turn key start engine.

FYI if its the first start of the day and have the key in acc. Click the drivers door unlock the engine starter will turn the engine.

Asking second opinion. Chevrolet dealer said for $400.00 to $550.00 they will let me know the cause not fix it. Cannot afford that! :(

Also check the battery grounds and connections all good.