Again, nothing happened.
That's really strange. I don't know how anything else can be effecting this other than add-ons.
It can't be the slayer addon, as you downloaded the latest, and I checked that on my own Blockland and it worked fine.
It can't be other add-ons as you tried running slayer on its own with a fresh addons folder.
Can you upload your gamemode_slayer.zip file as my only guess is that it's getting corrupted and causing the syntax errors