Apple M1 Boards & Exclamatory Error?

[ugamazing]

We've now created a stack of 10 boards that have the same issue, which we suspect to be CPU-related. The issue is very simple--the board will not boot to anything, only showing the exclamatory sign inside a circle. No amount of DFU/restore, wipe/erase, etc, will resolve the issue. No boards have physical damage. We went ahead and replaced the SSD nands on two boards (one 02020, one 02016) and the issue remained exactly the same. We are considering replacing the CPU on one of the boards using a locked CPU, just so we can see if it resolves the issue.

Has anyone else run into this issue and solved it successfully? It's been a very elusive issue on these and we would love to resolve it.

[ugamazing]

I have some new good information for this issue, for any others:

We took four 820-02016 boards that were afflicted by this same issue--no history liquid/drop, but with a sudden exclamatory symbol without the ability to boot to anything (IR/OS/etc). We decided to just wholesale figure this out, so we did the following:

1. Reflowed the CPUs on ALL FOUR boards; this RESOLVED the issue (for ~36 hours so far) on TWO of the boards.
2. On the two boards that the issue persisted on, we replaced the SSDs. NEITHER BOARD resolved after this.
3. We took one of the CPUs from the non-resolved boards and transferred to a working but locked board. ISSUE PERSISTED.
4. We did not do this last step, but I suspect if we were to transfer a working/locked CPU to one of these boards, the issue would subside as well.

So, this appears to be a CPU fault issue. Reflowing the CPU very likely is just a temporary solution, and I expect the failure is actually inside the CPU. I expect the two "fixed" boards to fail after some time, but this is not a certainty.

Conclusion is that this exclamatory-symbol failure is likely always a CPU failure and not related to the nands. It could be a different story in some cases, but I suspect it will be the CPU 95%+ of the time.