Getting ready for my usual trip to France.
SFO-FRA is on UA; FRA-TLS on LH
TLS-FRA on LH; FRA-SFO on UA

As a 1P, I can check up to 3 pieces, up to 70 lbs each. I only check one large suitcase that usually weighs around 55 lbs. When I check in at SFO and have my one suitcase interlined, there is never an issue.

On the return, I always get some flak from the LH agent because my suitcase is over 50 lbs. I think LH might set a limit of 50 lbs on intra-Europe flights but I'm on the first leg of a trip back to the US, without a stop-over.

What are the rules? It seems that they should be the same in both directions??? Or do they differ because UA sees me as a 1P and LH as a *G?