I'm unable to replicate this.

How do you have the addon installed? Are there any Lua errors? Does the issue persist if you remove all other addons?

This is due to the recent Gmod update, this specifically:

"Spawnmenu will automatically open UI of currently selected toolmode on when joining a server or starting a new game"

There's a lua error associated with when that happens to people, I think it's that the addon is unable to apply presets that are saved on the client or something cause of the change the update made. Here's the lua error:

[ERROR] addons/textscreens/lua/weapons/gmod_tool/stools/textscreen.lua:129: attempt to call method 'GetTool' (a nil value)
1. MakePresetControl - addons/textscreens/lua/weapons/gmod_tool/stools/textscreen.lua:129
2. func - addons/textscreens/lua/weapons/gmod_tool/stools/textscreen.lua:242
3. FillViaFunction - gamemodes/sandbox/gamemode/spawnmenu/controlpanel.lua:100
4. FillViaTable - gamemodes/sandbox/gamemode/spawnmenu/controlpanel.lua:89
5. ActivateTool - lua/includes/modules/spawnmenu.lua:287
6. unknown - gamemodes/sandbox/gamemode/spawnmenu/toolpanel.lua:132

Timer Failed! [Simple][@gamemodes/sandbox/gamemode/spawnmenu/toolpanel.lua (line 132)]

I have the same error here:
https://i.imgur.com/cml0tTz.png

It looks like you're using an old version of the tool. `MakePresetControl ` is an old method I don't use anymore, and those line numbers don't match up with the latest version of the tool.

I'd recommend always using the latest version of this tool by subscribing to the addon via the Workshop. See https://wiki.garrysmod.com/page/Workshop_for_Dedicated_Servers for how to do this on a server.

If you wish to continue using the old version, the underlying bug has been fixed in future versions of Garry's Mod as per https://github.com/Facepunch/garrysmod/commit/3a97c046747a16a8c4d7571d6daa38b539dccbc3. I don't know when this will land in a release though.

I'd still recommend using the latest version of the addon via subscribing to it on the Workshop though, to avoid these kind of problems in the future.