Debt system, apparently they did a 'mistake' on giving a bonus for reaching 4-5 bonds for each of every unit, which it should be 100 and 250, not 500 and 1000. So because of that, everyone who got the crystal beforehand, landed into Debt System for each crystals they got. That's why your claimed crystal disappear.
The bad thing is, in this case, if you manage to max bond all your achieved units before this Debt System implemented, you can't do gacha until next years.