XDJ-RX no 100% wet delay while mixing on headphones

Guys! I've just realised that it is not possible to hear 100% wet DELAY effect while mixing on headphones and it is somehow conencted to the 'headphones mixing knob' and 'cue'. Whats more, whenever I set the 'level/depth' knob to 100% and then turn the delay on, the sound is suddenly cut for about 1 beat. Is it just my unit or have I found a bug? Allow me to explain what i've also found :

1a. headphones 'mixing' knob - set to 100% master
1b. 'cue' button 1 & 2 - turned off
1c. applying delay effect - turning 'level/depth' knob from 0% to about: 25% - ok, 50% - ok, 75%- still ok, 80%- delay starts to fade, 100% wet - no delay at all !!!

I was curious what the hell is going on and here's what i've found next:

2a. headphones 'mixing' knob - set to 50% master
2b. 'cue' button 1 &/or 2 - turned on
2c. applying delay effect: 25 - ok, 50%-ok, 75%-ok, 100% wet-IT'S WORKING!!!! Turing on delay at pre-set 100% wet depth - IT WORKS TOO!!! As long as the cue button is turned on and the 'mixing' knob is set to 50%. Try to rotate it left or right - welcome back to point 1c - no 100% wet delay again.

SO the only way to hear 100% wet delay when mixing on headphones is to set the 'headphones mixing' knob to 50% and cue ch1 and/or ch2. Is there any way to fix that?