As for duplicates using the digital modes, it's pretty much automatic from the DXP standpoint when running Fox mode.  For instance, with WSJTx, when the DXP sends their RR73, the contact is automatically logged on their end.  If QSB played a factor on your end and you didn't get their RR73, you send your signal report again, the DXP may again send RR73, thus a 2nd logging of the original contact, just off by a few seconds.  They are NOT expecting a 73 (confirmation) from you in this mode.  So this can go on and on until you finally give up due to not hearing them at all.  Later, you hear them again and this time it goes through normally.  Now you are entered in THEIR log several times.  Some DXP actually do a dupe-check upon returning before finalizing their logs.  

This "problem" can be overcome if the DXP station uses ClubLog's LiveStream option.  That way, you will know within a minute or so, if you are actually in the DXP's log and not call them again on the same band/mode.  Now the wait begins for the QSL card or LoTW upload when they get around to it.  

In years gone by, on SSB/CW/RTTY ect., the DX stations would just say "sorry OM, you are a dupe" and not log it.  Today, the DX and DXP stations just log you and move on as there is no penalty for dupes no matter the mode.  Actually a time saver for them.  Plus, it increases their apparent QSO count.