i've tried with different imx53-QSB (4 in total, all equal) to power on and off very fast.
After 2-3 times imx53 enters Serial Download Mode.
It seems it doesn't recognize right the first 2K on Sd card.
To exit this status there are 2 ways, assert reset or shutdown, also waiting for power supply to die.
I use a hw patch posted here time ago to automatically power up da9053,
anyway even if you use power up button the result is the same.
On errata the only thing I've found was to set bootstrap pins to avoid fast boot and fast sdhc.
This was because of propagation delay on data lines of sd.
To reproduce the problem try to power it up very fast for at least 10 times.
da9053 works fine.
Maybe voltages timing are the problem.
Hope someone can help me.