Accuracy of position report via dead reckoning

[Rosco74]

Hello,
I just started a new carrer TWoS with the latest version 2.2.24.
First mission I left the Memel shipyard and went heading 240 toward the area of operation. There is like 10 hours of navigation at standard speed of 11 knots.
After several hours in sea I made my own position calculation. Simple as it was a straight line at 11 knots, wich is 20km each hour.
Then I ask the navigator a position report via dead reckoning, and his position report is like a hundread kilometers away ... wich is impossible. It seems the sub traveled almost 40kms each hour according his calculation...

To check that I saved the game and reloaded. Then you get a exact position of your sub. And yes my calculation was correct.

So my question is : any changes were made to the accuracy of the navigator in the latest version of TWos? did something went wrong because I never had such a big error in my previous careers?

Thanks

Edit : Yes I use Real Navigation