I have one problem with RadUpload and custom libraries. I have worked around many times and not get where is the origin of this problem. During loading my images the RadUpload is not Updating progress and after finish is sending one red error message similar as images that are soo big. I have tested many times and get some internal limitation to load only images < Height 450px. If image is more than 450px(451px)is not loading in my library. Library settings are allowed for size <5000kb no other limitations or webconfig settings. I have tested sizes and is not limiting. Actually i use one Global asax for limiting to 900px 500 px for Modules like suggest KB
article no other.
During the Upload, i can get the service in Console and no script error exist until end of Upload process.
I use one solution like this thread
It's possible to implement one external RadUpload handler to get more in detail the process and found the source of this issue.