The 0x059 packet governs communication of synthesis completion and may be the culprit.
If someone wants to confirm that this packet is used to communicate that a synthesis is interrupted during its animation, i.e. after the synthesis results are received within the 0x06F packet, then it's likely that SE never patched out the 'old' way to request synthesis failure with only the loss of your crystal.
Pure conjecture but possible root cause if that's what 0x059 is used for. Since the client governs communication synthesis completion post-result-receipt and pre-animation-completion, the exploit is likely somewhere in there.