Syntax error: unexpected token < in JSON at position, L 333

Dear Ladies and gentlemen,

by seaching for a new shopsystem i found Opencard and i´m a little impressed about the system.
Now i try to install it and after that i want to install a extension.
By installing i get the error which i insert in a picture.
It seems to be an error in Line 333 and 345 in the extensioninstaller.
Perhaps one of you have an idea how to fix it.

Thanks a lot

heitzer75