Mouse Side Bottons no More Detected

I've got a gaming mouse Zelotes T-90 I used to use mouse bottons MB4 and MB5 to activate items in game yet on the new client too. I can't tell exactly at which patch but it was about January 2017 when in some games those bottons couldn't get detected in-game. Now, June/July 2017, they are never detected in-game. I already resetted the input options from the config folder, as described on this site but nothing has changed. I can bound items to those bottons from the out-of-game options window where they are detected but, when I start a game, they do not work, nor can I bound 'em again in the in-game options window. It seems that somehow the in-game software is not able anymore to detect those bottons' inputs. The other mouse bottons are still working as they always did.