Hello and attention everyone with the boot-loop issue.
After searching for “SMSL DA-9” in the YouTube App, and sorting by “Date”.
I discovered about 4-5 videos about this boot-loop issue.
A person in one of these videos claimed to got a “replacement DA-9” which had the same issue, but also discovered that when they set the “Screen Brightness” to Maximum level and power cycling using the remote, the issue went away (as long as you leave DA-9 on Maximum screen brightness).
So it may be worth trying the following and see if it fixes it.
1. If stuck in boot-loop, power off at wall socket, wait, power on so you can get into the menu. Then set “Screen Brightness” to maximum level, turn off DA-9 with remote, wait, then turn on with remote (power cycle with remote).
2. If option 1 fails to fix: do the same as above, but after turning off DA-9 with remote, while DA-9 is “off/standby” turn off power at wall socket, wait, then power on with wall socket (power cycle with wall socket).
Then make sure “Screen Brightness is at Maximum and try power cycling with remote to test if DA-9 still has boot-loop issue.
Hopefully this can solve the issue for some people.
Although you will have to always use DA-9 with screen on Maximum brightness level.