Currency translation not working for just one period

Hi BPC experts,

I have an issue about Currency Translation. When I run a package for converting a currency for any period of 2015, there is no issue.

However, when I run a currency conversion for 2016.05, I get the following error message :

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I checked the input form in the rate model to be sure that there is an exchange rate for 2016.05 (see picture below).

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I also emptied the rate cube and put back the exchange rate but I still get the error message. Furthermore, the other periods of 2016 are working fine except 2016.05.

What could be the solution please ?

Thank you in advance,

Dat