I discovered buggy behavior w/ savePreference(). It creates the sys_user_preference record, deletes it, then re-creates the sys_user_preference record. This results in a discrepancy between sys_updated on and sflastRedirect, which  causes the copied record to be opened in a new tab once more whenever the user opens another form in the portal. 

 

This behavior does not occur if you insert the system property starting with GlideRecord('sys_user_preference').