2018 Silverado 5.3, starter slow clicking, no start

[AD907]

Hi all, this has been intermittent: replaced battery, battery distribution tray, starter and complete positive wire assembly to starter/alternator etc.  Truck started and drove fine, next morning won’t start. Starter slow clicks, all the lights and dash turn on and off with the clicks. It’s very slow and deliberate. Not the typical clicking with a dying battery. I’m at 12.7volts this morning after replacing the starter wire assembly, the truck would click once or twice but then start. I checked 4-5 times, next morning it’s back to square one. Prior to this, I notice the starter was having an issue turning the engine over sometimes (slow turning or delayed firing), once I’d turn the truck off, battery gauge would show the battery dropping into the 11volt range. I have check the relay, it tested good and I jumped the relay and the starter would spin fine. I’m at the end of my knowledge on this, I’ve searched forums and I’m not seeing anyone talk about the slow clicking. Anyone have any idea? Thanks in advance. 
***Update***
I replaced the negative battery cable and found a ground by the brake booster that wasn’t super tight, truck fires up with no issues now.

 

Edited May 5, 2025 by AD907
Update

[Snowcamo]

Go over all the ground wires and clean and secure. That's a great start. 

[AD907]

I’ve cleaned the 2 grounds off the battery, on the block and the other behind the fender liner. I have a new ground wire assembly that I will swap out, but I don’t think that will fix the issue. 

[mikeyk101]

Do you have a Range AFM disabler?

[AD907]

35 minutes ago, mikeyk101 said:

Do you have a Range AFM disabler?

No, mechanical AFM/DOD delete done last July.