Converting ttf to otf

[_Darrel_Fossett_]

I am trying convert a ttf file to otf but I keep getting the following error

Running txlib...
txlib: --- C:\crystal\Crysb___.ttf
txlib: (ttr) cmap: invalid idRangeOffset in segment[23] (fixing)
txlib: (t1w) multiple glyphs with the same encoding
txlib: fatal error

I can run the edit table command and it fixes the issue but when I go back and rerun the make command it fails with the same error.

[_Read_Roberts_]

Fomr the error message, I think the problem is in the source ttf font cmap table. It is permissible to assign one glyph to more than one Unicode value, but it is not permissible to assign more than one glyph to a single Unicode value. In the source data, yuou need to find which Unicode value has more than one glyph assigned to it, and then fix that