Do you have all three workshop entries activated while playing?

Yes I do have the game files 1/2 and 2/2 as well as the game itself installed if that's the correct term. Also while I was in there double checking, I deselected things like energy hands. I had several turned on. But I went back to the game and the giant yellow ERROR words were still blanketing the console.

Can you upload your savefile? I would like to load into it.

Yes, but I haven't been able to find it. What is the most newbie friendly way?

Thats a good way to find it:
https://www.yekbot.com/half-life-alyx-save-game-location/
So for example a complete path could be:
F:\SteamLibrary\steamapps\common\Half-Life Alyx\game\hlvr\SAVE

In this SAVE folder I only need the slot where you saved in.
For example the s5 folder if you started the game with Slot 5

OK I have S8 in my sights. Simply dragging the file to the discussion doesn't seem to work. What is the best way to upload it to you?

I got the same GIANT ERROR here

Just upload it anywhere and I can have a look at it. I have a solution in my mind for your playthroughs, but I would need to test it before.

Here is my save folder
https://gofile.me/3WTba/w5S8H2Gvu

In an earlier save I had the*ERROR* too. This happens when the game is updated and you try to continue the game with a save done before the "update".
My solution was:
1- first a file check
2- start the chapter new from the loading screen.
Error gone. This worked for me in this and also other updated HL:A mods :)

So, you would need to do what you posted in the comments?
https://gtm.steamproxy.vip/sharedfiles/filedetails/?id=3118673534

No, only to replay a chapter from a specific point. This is not related to the "Error" issue some players experience.

Just to illustrate my lack of any savvy, I would need very basic instructions on how to upload. Do I need a third party app for this because I see no "upload button" and I can't drag my S8 folder to this discussion.

PS I actually did start the LABS chapter new after deactivating my energy hands etc mods. Still had ERROR all over the color console.

Ok, I have downloaded the save file, but I do not see a good way to fix it for you whithout restarting the campaign.

@bekawe2016
In your solution, what do you mean exactly with that point?
2- start the chapter new from the loading screen.
Sorry, but I can't really follow