IMO, a "proper" hardened spring locator needs to be installed.
Again, either the cups that came on the heads as they were delivered by Edelbrock, or the Comp 4696-16.

Remove the retainer, spring, seal, and current shim.
Put the spring cup on the head, check installed height with +.050 locks.
If you need to reduce the installed height at that point, put any shims under the spring cup/seat.
Once the installed height is set, reinstall the seal, spring, retainer, locks.

I can't tell from the pic what are on the heads for seals. The heads come with
rubber "ring and band" seals. If they still have those, they can easily be worked up off the guide with a screwdriver, and then carefully slipped over the groove in the valve.
They can be reused, and will slip right back over the valve and guide.

As the heads are now, they are not properly set up.........so you can do it right.......or do it over/again.

"I" wouldn't run it like that.......but I'm not the one in charge of this job.

I can see by the "shadow" in the spring pocket that it appears the springs are moving around quite a bit.

Without testing the springs for myself, and seeing how the pressure starts to spike as the coils start stacking up, I can't say for sure if this is where the root of your failure lies.
However, I'm pretty confident it isn't helping matters any.

Much earlier on in this process you're going through, you should have verified what the actual net peak lift at the valve is. Then you'd have a better idea how close to coil bind the springs really were.

As I said in the previous thread, I feel the three contributors were, fast rate lobes, oil too thin, springs improperly set up.
Fixing how the heads are set up, and running different oil are relatively easy to fix.