If you have checked the thread I linked earlier:
I think there are not many people who have this issue. In fact you may be the first to have issues with the sensor panel.
It sounds like it may be a defective device.
A manufacturing fault.
If the camera lens has no condensation, it seems likely that the rear cover is defective.
Especially as there is no other trace of condensation as you say.
I would be sure to persue the replacement because it is not a common problem at all, as I said.
If you have any problems with Lemfo support you can let me know by private message with your order details and I will talk to them.
Pease get some very good resolution photos of the damp in the sensor windows because the one you have posted is good, but still not easy to see the issue.
My advice is to reassemble the watch very carefully and maybe get a short video of the diodes not working correctly and very good photos.
Don’t mention that you took the case off or anything like that and be careful that you don’t damage the screws or scratch the case when you put it together.
It needs to be replaced. Drying with rice is good if you were not going to try and replace it.
The issue will reoccur so drying it is only a temporary fix.
Cheers