Bond Pricing of Italian BTP

I’m new to Strata,
I’m trying to price Italian BPT (fixed bond) and don’t understand how to set dirty price for calculating irr.
If I set , for examples, a dirty price to 98.00 (relative to a coupon of 5% and face value of 100.) a notional to 100, strata calculates a negative irr. If I set dirty price to 0.98, it works fine. Whats is wrong in my example?
Nobody can help me?

As indicated in the DiscountingFixedCouponBondProductPricer, Strata works with decimal prices (this is the case not only for bond prices, but for all prices). The prices should then be indicated as 0.98 to represent 98% of face value.

Thank you for your reply!
Another question. How can I manage govt bonds which have a redemption value other than par (eg italian govt bond BTB)