Do you have any other workflows and if so do they have the same issue? Trying to see if seem specific to WO as we haven't noticed this issue nor have we had something like this reported yet. I saw this APAR (
IJ17857: ROUTING WF FROM WF INBOX DOES NOT CHANGE STATUS (ibm.com)) which is listed as fixed in 7.6.1.2 base. This was a fix for a regression caused by APAR IJ08188 (
IJ08188: WORK LOG IS NOT SAVED IF THE WORKLOG TAB IS EXISTED IN THE WORK ORDER TAB. (ibm.com)). Both were specific to WO workflows so it's possible that it's still not quite right.
I don't have a workflow on WO in our environments for testing but it sounds like you may have an IBM bug. Something like this is probably going to be difficult to resolve yourself, so opening a case with IBM is appropriate.