I never ran nodes from Syno UI. I always used putty/SSH/CLI to install and run the nodes as root (sudo su). You don’t have to keep the terminal open ;). Just run the node and close the terminal (putty or whatever) by typing exit 2 times if you were in sudo su. Check my post for the commands.
The terminal is just a way to send commands to the linux kernel; the commands and programs started don’t live in that terminal, like in a windows program.
Never had a locked db or sudden crash. But my hardware is new; maybe if you have old or sh hardware, there could be something defective.
https://forum.storj.io/t/my-docker-run-commands-for-multinodes-on-synology-nas/22034