As per your email, you mentioned that if you go to Proposal list and select the proposal for Fred Flinstones and click the print button, you get error mentioned in above post.
You also mentioned that if you try the same thing in Method classic, by going to opportunity list and select the opportunity for Fre flinstone and click the print button, it generates the report.
I tried it and it works fine in Classic but gives error in V2.
I am going to create a ticket for the development team to have a look into this and I will keep you posted on the same.
-Inder