15" i7 2015 MBP with Iris Pro GPU, runs great except startup

I'm looking to see if anybody has tips for correcting choppy, inconsistent start-ups.

Like I said in the title, it runs great. Very occasionally I have some freeze-ups with higher end apps. That's rare. The problem is when I do need to restart or shut down for some reason.

1. When the unit goes to start up, it will often get to a bare sliver of the progress bar—maybe 3%—and then hang up. (There are times I experimented letting it go for an hour or so in this state and I get nothing. So now when I see this I just shut it down.).
2. So, I force shut it down from there and power it up again. At this point, it will usually go to about 25% and hang up. (I've also experimented with this state, and it goes nowhere.) So, when I see this I force shut it down and power it up again.
3. At this point, I will get a thing where I power it up and it instantly flips to a kernel panic. This is where it gets weird. When I see the KP I know I'm getting closer. Like, I've crossed some barrier.
4. From here, sometimes I let the KP clock down. And sometimes it will re-start. When I see the keyboard lights go on, the cursor appears, and I get to my login screen. Okay, great. But sometimes it takes me back to #2.
5. Sometimes I don't let the KP clock down and I "hit any key". When I do that, sometimes the keyboard lights go on, the cursor appears, and I get to my login screen. But sometimes it will go to #1, #2, or #3.

Once I get the thing running, it's great. And I rarely have to shut down anyway so it's not a huge deal. It's just that starting up can take about 10 or 15 minutes as I bounce through all of the different states it might land on. I spend that ten minutes reading the tea leaves and trying to figure out which kind of startup input it wants next.

I have also tried to restart with <option> and selecting the EFI. That doesn't do anything different which suggests to me that the unit is doing a fine enough job picking the EFI and then the correct OS. Something in the middle is just... fussy.

I'm curious if anybody else has similar issues and if/how you were able to solve them.

I'm posting this full well knowing that I'm playing stupid games and may be getting stupid prizes. I also realize that otherwise I'm having very good performance relative to all the things that could go wrong with an OpenCore Hackintosh.