You mentioned that the original hold open worked flawlessly before it broke. This one seems to mostly not work. It seems to me this fact set isolates the problem to the new hold open part.
You also said the hold open spring on the new part is interfering with the operation of the barrel/receiver assembly. That is not supposed to happen. You might consider posting a photo of this new hold open, in the meantime I think your idea of trying a new hold open spring is a good one. I'd also mention I once had a hold open that was not rising quite far enough to reliably catch the breech bolt on last round, polishing the HO fixed the issue.
Also I would try a hold open from your other Luger and see if that works, as well as trying the toggle assembly from the other pistol.
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