I had this earlier today. Made a couple screenshots that ill come back to post once im at home. Had a game against Voorhis.
Also i posted earlier a bug with Albrich making a 3rd copy of a card, although its a ghost copy (cant use the 3rd card).
This time i had several ghost cards, some of which were copies of cards i had in my hand already. It seems any kind of tampering can trigger this, such as mulliganing the cards in question (although i cant confirm this theory), moving the cards order in the deck, and the oponent revealing one of them. This makes sense because most of the cards i had this issue with last game were revealed by Voorhis' ability.
Here's where the gamebreaking part comes in: lets say i have leo bonhart and alba armoured cavalry and a number of other cards in my deck. If alba is the top card in my deck and leo is the 10th card, moving leo to the top and alba to the 10th spot will make me see 2 leos in my deck, but the 10th card is actually still going to be alba cavalry, although i wont know it. This happened to me in todays game against Voorhis, but i dont know if it was caused by albrich or voorhis reveal. Royal Decree and Jan calveit's ability will show the REAL card (alba in this example) but previewing the deck will show a fake 2nd gold card or 3rd bronze card. If its only one ghost card it can be problematic to know which card it actually is because in my case you cant unplay royal decree or calveits ability, and have to look at all the cards in your hand, graveyard and your deck and make an educated guess as to what the bugged card might be. This becomes impossible when you have (as i experienced and i will post the screenshot of it later) 2 or 3 Vrygheff (golden card) in deck and one in my hand.
Another bug i noticed with the reveal mechanic is that spotters for example always reveal the same card or another one but they bug it to look like the first revealed card and will always boost by the first cards power. I made a 41 power spotter by using vrygheff and 2 ointments and revealing the same 10 power card in my opponents deck 4 total times.
TLDR: yes.