Team Fortress 2 Server Supporter

There are several server options that affect weapon damage in Team Fortress 2, and they're often confused:

Weapon Spread -- With this turned on, hitscan weapons, such as shotguns, will have the same non-random pattern of "bullets" each time they are used. Default is ON.

Damage Spread -- Each weapon normally has a minimum and maximum damage. No Damage Spread means that each weapon will do a set, average, damage rather than varying between attacks. Default is ON. (Critical hits always do 3 times damage)

Damage Falloff -- Normally, the damage dealt by a weapon decreases the farther away you are for your target. If this is turned off, A rocket detonating right next to you and a rocket shot from the opposite side of the map will do equivalent damage. Crits are never affected by Damage Falloff. Default is ON.

The default is to have Damage Spread ON. Nodmgspread refers to servers which have turned it OFF.

In order to avoid it I suggest to not try entering more than once in the door of specified team, if the first time fails selected random.

Anyway, if it happens that you got stuck, you can easily recover from this bad situation by opening console and write

retry

Retry command force a server reconnection and you access again the team selection screen. Sometimes, on busy servers with many people try connecting, this command causes to lose the slot.

For this reason, as suggested by @Dave McClelland in comments, is preferable use the command

spectate

because it fix the problem without forcing a re-connection.

If you really want to join RED or BLU team and reduce the probabilities to trigger that annoying behavior, I suggest to wait that half or more users on the server choose their own team, and then try enter your desired door.