Set field value does not work for unlimited text field

Hello

I creatio sales, i am trying to set field value from another entity.

for opportunity product, i try to setup its values from the price book record.

when i do that for the price itself - it works great.

but when i try to do this to the description field (unlimited text field) - from one test field to another - its not working.

The 2 fields are the same field type, and the page that i try to insert the value from is the same as the one that i use to take the price... 

Does anyone bump into this issue ? 

Thanks in advance... for any comment :-) 

AGK