I totally agree, the upper chamber can and should make amendments to legislation. In this case, they made a generally good amendment to the Employment Rights Bill (allowing "at-will" dismissal up to the first 6 months rather than the initially proposed total ban).

However after that amendment was accepted, Conservative Peers (who hold a majority) initially voted against the bill again: https://bectu.org.uk/news/prospect-slams-house-of-lords-for-...

It was eventually passed a week later when the Lords accepted the Commons amendments but that second block on 11th December shouldn't have happened.