Now I can say for sure that the problem begins with 21.08.
Armbian_21.05.1_Orangepiprime_focal_current_5.10.34_xfce_desktop boots up fine, 40+ tests of booting.
OPP and other content of DTS are not the cause of the problem, I have tested it.
Also I have tried another available kernels with 21.08 (5.4, 5.13, etc) and the same problem of boot stability was occurring.
Also I have tried to flash 21.08 into another SD card, the same problem was occurred.
It would be good if anyone identify the difference between 21.05.1 and 21.08 that causes the unstable booting.