Are you sure you don't have in camera cropping set?
Look in your users manual to see how to check if you do.
And can you fix the crop in LR or not?
You may have set a custom default of a square crop inadvertently when you though you were setting other defaults, only. Setting a custom default will take almost ALL the settings, so you should be starting with a newly imported image to which you've made just the adjustments you want to save as defaults.