I have found that if I install an xilinx card in an older s9 to install brains the holes don't match up.
This causes the ipreporter button (on left) to be pushed in all the time.
When that happens the boot cycles constantly.
I take off the little front plate on the controller board carrier. Then it will boot successfully.

A corrupt or missing cgminer.conf can cause issues as well, won't start cgminer.

I have had ssh access not available when trying to fix the cgminer.conf.
Had to enable DROPBEAR through the gui to get ssh access.

Another anomaly- running Kaspersky on PC that is using the gui configuration page.
Kaspersky blocks, so you cannot change anything on the configuration page. (pools!)
I just disable Kasperky and then fix the configuration page,  then enable Kaspersky.

Running on 100+ miners, VERY STABLE.

With the 6/5 Braiins firmware pushing the image to the SD card , changing the jumper to boot from SD,
I can use the GUI from the SD card to flash the NAND and fix cgminer.conf missing, and other problems.
The GUI only has the flash option on the 6/5 firmware running from the SD using the new image.

I can pretty much mix and match any s9 hashboards with Braiins. Mixed S9 with T9 boards also(s9 form factor)
Just a wonderful piece of software.

Does braiins work on T9+ yet?
Thanks.