I join my server and half the people are invisible on it. Seems like they go invisible when they purchase and turn nightvision on.
I tested it out for a bit and it occured once again when I enabled the nvg.
I did amx_nvg 1, lights got turned off, but not a single person in the server got nightvision.
Then I set it back to 0. Restarted the round and did it again. This time only 1 person got nightvision while the rest remained in the dark.
On the 3rd try everyone got nightvision, but one of the CTs became invisible.
I disabled the plugin for now to see if the invisibility happens again, but its most likely the plugin.
EDIT: Apparently it is still happening. I will try to figure it out and I'll let you know what was causing it.