I actually have that **= error code as well but in my case it just straights up boot to OFW when it does fail to glitch.
Out of 20 reboots, theres a chance that 1-2 times of it gets a failed glitch with **= error code with my OLED switch which leads its a dat0 issue? but the connections are good they said.
I already sent it to get it reworked by the installer and it seems the error doesnt go away, the emmc is reballed with that green pcb adapter sandwich in between the motherboard and the emmc chip. they also go as far as changing everything and go as far as reballing it for the 2nd time with the same error.
in the end, i just lived up with it and its only like 1 out of 20 tries it failed to glitch anyway. I also flashed the rp2040 with 2.75 firmware linked here, tried downgrading to 2.73 and the error becomes erroneous this time and basically randomly throw error codes all over the place every time it fails to glitch and boot directly to OFW.
fast forward to this day, my OLED switch is now swapped out with HWFLY modchip instead, not a RP2040 based, and this time, the glitch never fails. same wires, flex cable on cpu is also the same, just different modchip.
So my speculation is that, rp2040 maybe needs more research to deal with this issue not glitching some of the switches or have erratic failed glitches.
The thing with rp2040 is its simply cheap.
hwfly used fpga which is way more costly compare to the rp2040.
rehius just do something that for me is a 'magic'.
i laugh at first, for me, its impossible for rp2040 could contend with fpga.
But he did it anyway, and worked.
You have no idea, how awesome is that.
This is achieved by overclocking the rp2040.
Of course stability wont be as impressive as fpga with a dedicated clock.
But again is way cheaper than fpga.
Right now the cheapest fpga we could play around is made by sipeed.
And the time invest is not worth at all.
I rather stick with the cheap rp2040.
For people that want perfection just used fpga,
For me its not worth spending money for a perfect Boot probability.
I rarely boot my switch, just play the game.