I am using version 12.9. When attempting to choose "Accept as solution" for a KT document for an issue, I receive this error. I also see this message in the stdlog:
ktweb.spl kt_link_unlink_kd: AHD03029:Bad_param in Dob_by_id on iss
I am able to choose "Accept as solution" for requests in the ticket system.
We have also applied the Cumulative 1 update.
The last time that someone has successfully chosen "Accept as solution" for an issue was the day before the 12.9 upgrade.