Report the invalid spawn points you find in the FFA DM servers here, so we remove them.
If you find one, open the console, type "cl_showpos 1" and hit enter. Your current map coordinates (X, Y, Z) will show up at the top of your screen (after "pos:"). Note them down and post them here including the name of the server.
You can consider a spawn point as invalid when you spawn e.g. outside of map or somewhere you can't move.
You can disable your current map coordinates that are shown at the top of your screen, by opening the console, typing "cl_showpos 0" and hitting enter.
To respawn type "!respawn" or "/respawn" on chat. Otherwise open the console, type "kill" and hit enter.