I love Rhododendrons and used to grow several sp/hybrids/cultivars.
There are 1,000's and even Rhodo experts struggle to name them/do not always agree...even when the specimen is in front of them.
I live near Glendoich where 3 generations of the Cox family collected seeds and started a nursery specialising in Rhodo's.
Many factors come into consideration.....time of flowering/shape size of flowers /colour of buds compared to open flowers/shape, size of leaves.
Inudendum etc etc etc.
this is merely a suggestion/my best guess.
Leaves are enormous.