Here’s a pretty basic tip which you probably knew/figured out already. But, just in case it didn’t occur to some players, we thought it best to remind them.
This probably happened to some players with regular gems even before the season, as moving them around your inventory without paying too much attention can lead to them being stuck in socketed items. However, while that isn’t a problem for regular gems, which can be unsocketed, it’s a big problem for Malignant Hearts. If you get a heart stuck in a random inventory item, you can’t take it out again no matter what.

So, be careful when moving them around socketed items! We wouldn’t want you losing those valuable Wrathful ones or a high level one you need for a build!