Hey there, A while ago, when i did my personal solo and later solo flawless completion i had the same issue as you. It seems that there was a bug with the solo triumph and the flawless one that wont award you the triumphs even when completed. Completing the solo flawless triumph seems to fix everything and awards all triumphs linked to it. Needing to complete solo flawless run in order to get the solo and/or flawless run might not be ideal but its the only workaround i have found. Best of luck.