Must shut off truck to use 4wd.

I don't see anything that looks questionable to me. I'm using the zoom on my phone to look it over slowly.

Not that I really know what I'm looking at or for other that something that looks off\ununiform.

 

A cracked solder joint would look something like this.

 

Maybe @Chocolates can work you a deal, if it comes to that.

Same Part#....

https://www.tacomaworld.com/threads/add-actuator-and-4wd-conputer.846191/

 

I can't find anything that looks suspicious to me.

I'm going to reinstall this bad boy and monitor the situation better than I had.
Thinking back to around 2016 I remember a day when 4wd hadn't engaged properly at the beach. The truck looked to be in 4wd (as per indicator) but when I got stuck I noticed my front wheels weren't participating. However it was too late by that time since I was stuck. That's the only time I can recall actually having an issue.
They say to never look a gift horse in the mouth.

 

Well it was worth a look anyway.

 

Always a good day learning something new. Reinstalled and tested. All works as well if not better than it had when I started this post.

 

Maybe it was just some terminal fretting in the connectors, have to see what happens.