Many digital cameras prepopulated the "Caption" field of images. My Olympus annoyingly does this with "OLYMPUS DIGITAL CAMERA", and this is one of many cameras I've owned that has this "feature".
Luckily I can create a Metadata preset for Import in Lightroom that sets this field blank. However, when these photos are then later synchronised to LR Mobile, this field gets reset back to "OLYMPUS DIGITAL CAMERA".
As each photo is uploaded the Caption field gets populated. I suspect it's copying the value from the "Video : Description" field which has the same manufacturer's prepopulated text.
Camera prepopulating Caption field:
When LR Mobile uploads, I think it is looking (wrongly) at this Description field even if you've set Caption to another value: