Double dash in Lyx 2.2.1 is not printed correctly

[Danko Georgiev]

Hello,

I have just updated to the newest LyX 2.2.1. and immediately got a 
problem with automatic conversion of double dashes -- to en-dash in a 
manuscript written with Lyx 2.1. This en-dash replacement resulted in 
error message in index sorting when compiling PDF.

When I found that en-dashes appeared in the manuscript, I replaced them 
again with double dashes (as this was the case in Lyx 2.1). But then the 
compiled PDF by Lyx 2.2.1 shows double dashes in the PDF instead of en-dash.

I did not find an explanation of what is going on in internet, so 
decided to share this problem with the lyx users list

Any advice how to restore the old Lyx behavior in version 2.2.1 would be 
appreciated.

D. Georgiev