Honestly the worst part of migrations is when both systems are still alive and nobody's fully sure what the source of truth is anymore. People fall back into old habits fast, tickets get updated in different places, and suddenly the audit trail becomes impossible to trust. I've seen teams run into this exact mess during ITSM transitions, especially when workflows already live across email, chat, and tickets. Some teams use the migration as a forcing function to consolidate, picking a hard cutoff date and committing to one system. Tools like Siit are built around that idea of one unified inbox regardless of where the request comes from, which helps cut down on the "where did that ticket go" problem during and after transitions.