AFP with custom font TTF generates space-letter-space

I am producing an AFP file with Apache FOP 2.8 and java 17.
In my fo.xconf file am using a custom font with the TTF format and I have used also a xsl file. 
I have tried several TTF and tried also the attribute position-by-char="false".

Altough the file renders properly when viewed with a tool like "Papyrus AFP viewer", 
I have noticed that the content has issues when analyzed using AFPexplorer.
In the example below you see that the words are not generated words by words but space-letter-space which is causing problems when printing.

FPexplorer
MDR:  1= A r i a l  2= a r i a l N  3= a r i a l N
 
PTX tag:
 A  r  i  a  l  a  r  i  a  l  N  a  r  i  a  l  N  B
ESC
AMB   223
AMI   236
SCFL  1SVI   11