Do you have the source code from which the .class was compiled? Note that Kotlin supports inline functions, and when a method calls an inline function, the code of the inline function and the code of the lambda passed to it will be compiled into the calling method. In that case, the lines from the inline function will have line numbers outside of the range of lines in the original source file, and the SMAP table will contain full information on the line number mapping between all source files involved.
There should be no cases when we simply omit the line number information.