File > Export doesn't remember the previous setting of Resize To Fit when Image Format is DNG.
To reproduce on LR 14.3.1 / Mac OS 15.5:
1. Select any photo.
2. Do File > Export, with the the File Settings options Image Format: DNG and Use Lossy Compression, and the Image Sizing option Resize To Fit: Long Edge, 3000 pixels:

3. Do File > Export again, and observe that Resize To Fit is unchecked.