Showmessage doesn't appear:
There can only be one gamemessage on your screen at one time. LVP is using an area-name announce thing, this appears in the lower-right corner of your screen, gametext nr1 for example, when you use /showmessage at that time, it won't appear because you got two gametexts then. So it won't appear on your screen, but it does for the other clients. There is not fix for
Unknown command:
I never noticed this bug, maybe it only happens to normal players. I'm just looking at the code, there is an inaccurate part. So when two people at the same time try to use the showmessage command, only one of them can use it. I will fix this.
Thanks for reporting!
There can only be one gamemessage on your screen at one time. LVP is using an area-name announce thing, this appears in the lower-right corner of your screen, gametext nr1 for example, when you use /showmessage at that time, it won't appear because you got two gametexts then. So it won't appear on your screen, but it does for the other clients. There is not fix for

Unknown command:
I never noticed this bug, maybe it only happens to normal players. I'm just looking at the code, there is an inaccurate part. So when two people at the same time try to use the showmessage command, only one of them can use it. I will fix this.
Thanks for reporting!