Bonnie/Scrambler oil leak

Hi, has anyone had an oil leak problem with an 865 engine that seems to come from the front by the sump plate? My 64 reg bike started leaking 2 weeks ago, the dealer did a visual inspection and said the leak was from a plug inside the engine behind the starter. This threaded plug is only used for engine assembly. The fix worryingly is to tighten it up or possibly put PTFE tape to seal it.
I've put a longer post in the scrambler section, but this ''fix'' worries me.

Anyone got experience of this?

Trev