The issue below has been confirmed.
We are currently investigating and working to address this issue.

[Known Issue]
■If a portrait was linked with multiple gear sets before Patch 6.2, the data for the portrait of the linked gear set will be shared. And when that portrait is changed, the data of other gear sets that share the same data will also be changed.

*When addressed, the cause and situations where this issue has already occurred will be automatically resolved together. For a temporary measure until this is fixed, deleting the affected gear set and creating a new one will resolve this issue.

We sincerely apologize for any inconvenience caused.

*Edited on Nov. 23, 2022 at 7:35 p.m. (PST)
The issue above was fixed during the maintenance that took place from Sep. 12, 2022 at 7:00 p.m. to Sep. 13, 2022 at 1:50 a.m. (PDT).
We apologize for any inconvenience this may have caused.