Scoreboard objectives don't work properly with command parameters

When a scoreboard objective is created (scoreboard objectives add example dummy), all players scores are set to '0' by default.
Then a command is used (e.g. /tp @a[score_example_min=0] ~ ~1 ~) and the result message is 'the entity UUID is provided in an invalid format'.

I cannot tell what the problem is, whether it is player parameters are broken or players just don't have a scoreboard value assigned to them. This is breaking a lot of my maps and I would be grateful for a fix.

Thank you.