I think the reason you're seeing that is because "_LL-WGS84-0" isn't a coordinate system, "LL-WGS84" is.

The reason why your reprojector wouldnt be fixing it is because you're trying to reproject, and because the feature isn't is a valid coordinate system it can't reproject.

What you need to use instead is the coordinatesystemsetter. All this does is set the coordinate system. It doesn't reproject. So if you used the coordinatesystemsetter on a feautre that is in NZTM (my local system in meters) and tried to set it to LL-WGS84 (DMS) it would do it, but when you look at the data, it will be all wrong as its looking for coordinates that are well in excess of the -180 - +180 bounds of LL-WGS84

Hello I have the same issue with another Projection. It seems that FME added itself the _0 suffix giving Unknown coordinate system '_Lambert93_0' specified - aborting while the transaction is actually working and the inspector actually showing the entities.
Even placing a CoordinateSystemSetter in front of the inspector specifying EPSG:2154 doesn’t correct the issue.

Hi ​@benoitda this is a fairly old post, in the future I would create a new thread with a link to this post as a reference to the problem you are facing. This would get more visibility as comments like these often get lost. When creating your new thread could you also include information regarding your version of FME, log file, what reader/format you are using, and any additional information would be helpful too! 

OK for the next time, but as my problem is exactly the same and no answer was given I made this choice.
My version of FME is 2021.2 Build 21806.

I join a exemple, when executing with cache enabled, everything is ok until the Preview renders the data and then the log window display the error.

PS : a pity this forum doesn’t allow for .fmwt files to be uploaded...

I found the origin of the problem :

I had previously used the “Mark location” feature in the Data Inspector. It was fixed with the coordinates that appears in the log. In the window of the Mark location, the coordinate system is written as “_Lambert93_0” that’s what cause the trouble.

Each time the Data Inspector is called, it tries to render the point and raise the error.

Removing the values in the Mark window get rid of the error.