If returning it to Ruger is an option, that is how I would proceed.
However- if it turns out it isn't an option, then from your description " there is some play in the transfer bar…". If this is with the hammer down, trigger depressed so the transfer bar is in the "up" position, I would guess the hammer nose needs to be shortened.
Ruger does have a transfer bar assembly that is thicker and compensates for what you are describing. This one came off my mid frame flat top originally. I'll attach a picture.
You can see how the end where it contacts the firing pin is thicker.
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By "Hammer Nose" this is what I am referring to, indicated by the pen. Shortening this portion effectively decreases the depth of the notch below it. The transfer bar is impacted by the area of the the notch. If you have a way of measuring the thickness of the transfer bar and then the depth of the notch, if there's a big difference that might give you a clue as to what's happening.
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