Unable to find a sign

OK, I've recently just discovered this plugin to populate on my server. But I've come across a problem. When I place a sign on the wall. Sometimes it puts the image from my url onto the sign & sometimes it says, Unable to find sign. Move closer & so forth. I'm close enough to edit it the normal way, so I should be close enough to use the /sil <Url> command. I've made a pretty big base with walls, I've placed xl & xxl frames on my walls. But even though 1 frame is next to the other (for testing purposes) 1 will allow me to do it, the next wont & maybe the next 2 or 3 & then it allows me for the remainder. 

Something is preventing it from always detecting signs. Are signs limited by distance from the TC? If so, it shouln't be. So long as I can place the painting, I should be able to put my image on it.

Does gdiplus.dll need to be loaded on a windows host for sign artiest to work? Maybe not this might be legit a issue with the mod. I am for sure wanting to get this working and I have not found a fix at all. 
If the image you are using is not the exact size of the signs, it’s have to be resized. I believe that library is used on all OS types for this.
Well, I can understand this. However, I did say that I tested this out by placing the multiple signs next to each other, gradually getting furthe away from the TC. The same image onto the same sized signs. Some add the image, but when I get so far away from my TC, but still within the building priv zone. It stops working. It's not the sign & image size problem. For no reason I can think of, other than distance away from the TC, the plugin fails to detect the sign.

Here's a video of what I'm referring to.
https://www.youtube.com/watch?v=2z1Pa9YLk5k

OK, I've sorta worked it out by adding a debug to the plugin & apparently it's to do with raycast is reporting back autoturret....ignored the sign and wall. As I have a turret on a platform, with 2 walls on either side. But if there's a turret directly behind the wall, it ignores the wall, sign & picks up the turret.

Anyways, It Seems like casting from player.eyes.HeadRay() isn't reliable anymore. Because if my line of sight is at a turret placed on my structure anywhere, even if its on the other side of the building. It seems to only see the turret. As if I look down at the floor, through the picture frame or up into the sky, it works. 
It is very difficult to pose a picture impossible to see. How can I do it thanks

https://youtu.be/US8LT8ehC3U
I have seen that at times but am not sure of the cause.  I can only suggest trying different angles.  Also, be sure that the sign isn't locked, etc.
In response to rfc1920 ():
I have seen that at times but am not sure of the cause.  I can only suggest trying different angles....
Just out of curiousity, what value are you using for "Maximum distance from the sign" ?
In response to rfc1920 ():
Just out of curiousity, what value are you using for "Maximum distance from the sign" ?
For what it's worth, I have mine set to 10.  If looking up to the sign I still have issues but head on is no problem.
I experience this with XL Frames. It's very hard to find a spot where the frame accepts your picture.
I set the distance to 10 too. No change.

Just in case someone else is experiencing this. noclip may be a cause too.