I've had this problem that presented twice so far, sometimes when picking in and out eternals from the bank, either they disappear or a random number of them comes out. The first time this has happened i pulled put 10 cristallyzed fires, then i clciked them to get back in the bank and only 7 made it trough. Today i pulled out 10 crystallized water, turned them into an eternal and tried to put it back in the bank and it disappeared entirely. I've tried reloading ui and logging out and back in but its still nowhere.
I dont have a screen because my first instinct was reloading ui thinking it was a visual bug, but its the second time this has happened and i think its an actual bug.
i dont really care about the item, essence of water is worth like 2g anyway, but im worried this might happen with some more expensive item and i wanted to report the issue. I think this is a thing specific with crystallized-eternal essence because its the only kind of items i've ever had a problem with
Does your bank have a bag with that item somewhere that you're not checking? They may be stacking up somewhere and you not noticing that.
If your bank is as disorganized as mine, that's most likely the answer. That's why I like using bagnon because it shows the total count of that item that you own and you can filter. Sometimes I can't see where it, but using search I can find it more easily and see that the number is still the same.
If you're sure it's a bug, record a video and open up a bugreport. If that is the case, this is a much worse bug than it seems because people will lose more valuable items than eternals.