I’m not familiar with the radio you’re having issues with, but if I remember correctly the AM stuff I have has different transmitter output levels by model/brand. Which definitely impacted performance.

Another possibility is how well each radio set is matched to its correct frequency, it’s not just the crystals that control that. Do you have any old school airplane shops/clubs in your area? I used to have my stuff individually tuned by an experienced airplane guy. Wasn’t very expensive or hard, basically just adjusting trimming pots to get maximum signal while reading an oscilloscope. Doesn’t have to be an airplane guy of course, but they do seem to be very concerned about radio performance for some reason.