1. In Library, select one of the problem photos. In the Metadata panel, select the Location tag set and verify that there coordinates displayed in the GPS field.
2. In the Export options, ensure you've selected Metadata > Include: All Metadata and the option Remove Location Info is unchecked.
3. If those don't help, in Library select one of the problem original photos and do Metadata > Save Metadata To File. Upload the photo and its .xmp sidecar (if it's raw) to Dropbox, Google Drive, or similar and post the sharing link here. We can test whether other LR configurations export the coordinates correctly.
I have come up with a workaround. I usually export my edited files to a new folder as JPGs. At the moment I'm mainly using my iPhone 13Pro Max. No GPS Data in the new files. If I instead export them to my 'Edited' folder as Orignal, the Gps is attached. I can then export them to my Flickr folder as JPGs and the GPS data is still attached. If I export the file direct to Flicker from the folder with my original imports, NO GPS data.