Mortgage interest deduction less than mortgage interest paid

I have a rental property, and I noticed when reviewing my federal return that the amount of mortgage interest deducted is quite a bit less than the amount of mortgage interest I paid during the year (~$18K deducted vs ~$37k paid). I've itemized my deductions so I'm not sure why there's such a large difference. My loan is above $750K but only by about $50K, so I don't think that should be the reason for the large difference?

 

I do have a slightly more complex situation with this rental where I rented out a few rooms while I was living there from Jan - April, then rented out the entire home starting in May, but I don't think that should affect the mortgage deduction? I also have 2 separate 1098s this year as my mortgage was transferred to another lender but one 1098 is for ~$34K and the other is for ~$3K, not sure if this has anything to do with this either?