Item not providing stats in battle (?)

Not sure if this only happens with Mahuxotl's Machination but today i noticed that the core bonus is randomly deactivating, thought that maybe it was a loading screen issue, where my str points on the tree didn't register so i unequipped/equipped and the bonus activated again, kept double checking my rarity during multiple runs and noticed that it seems to be deactivating mid battle as well (rarity cores, spark build and no i wasn't gear swapping at that time)