Recently flew HND-FRA-ATL round trip on LH and used the upgrade bid option for FRA-ATL to upgrade to Premium Economy on the outbound. I opted to pay for a cash upgrade at the gate to Premium Economy on the return flight ATL-FRA. My original fare class was V, and the outbound was upgraded to E with the bid upgrade but the gate upgrade stayed in V on the ticket. I didn't notice this til I was already back in HND.

Miles posted exactly like the above:

HND-FRA (V)
FRA-ATL (E) (bid upgrade)
ATL-FRA (V) (gate upgrade)
FRA-HND (V)

I was under the impression your fare class was also upgraded even when paying to upgrade at the gate? I'm not sure what to do if they made a mistake as I credited my miles to NH. Does anyone have experience with gate upgrades and fare class?