Research efficiency problems

Hello, a friend has encounter a problem with the research efficiency when researching a vehicule 1 rank below the one used on the match, this seem to be a bug because on the stat cards of the vehicules it states that it shouldn’t get a penalty to research, here are some screenshots of the problem:
(Also forgive me if this isn’t the place to report this type of problem it is my first time doing so.)
Captura de pantalla 2025-05-09 165823

This other screenshot shows that problem doesn’t exist when researching 1 rank above:
Captura de pantalla 2025-05-09 185622

And here are the stat cards that state the efficiency of the research of the vehicules used:
Captura de pantalla 2025-05-09 191927
Captura de pantalla 2025-05-09 191936
Captura de pantalla 2025-05-09 191947

Thank you for taking a look at this problem and please tell me if this is a bug or perhaps the stat cards are incorrect.