Emergency landing - oil pressure drop - the plug is unscrewed.

This is a first!

How many hours are on the engine?

What is the engine S/N

Was the stator changed recently that involved the removal of this bolt and the ignition housing? Is it possible that it wasn't re-torqued properly during install?

https://legacy.rotaxowner.com/si_tb_info/serviceb/sb-912i-006.pdf

Thanks!

1. Yes, this is the first.

2. 1230 hrs

3. 4417144

4. The stator was changed about 250-300 hours ago. Later, I can see exactly when the stator was changed. I'll ask the mechanic how he tightened this plug.

It is exactly the same story that happened with me this week. I have seen the smoke in the cabin with the smell of oil appeared. After the oil pressure dropped to minimum. It was my luck that I fly at the moment not far from the airstrip and could land alive and not in fire. The plug screw #940520 was absent, hoverer its didn't show any sign of leaking oil before the flight. 
The engine was produced in 2014, 590 hrs, sn 4417326

The same questions still apply to your situation... See above (When was the stator changed etc.) 

This bolt requires 28 FtLbs, so it's not a small TQ value!

Also, some people use this bolt to rotate the crankshaft, and it can become loose if this method is used! 

Service bulletin-912iS-006iS was performed 20.09.2016 at 262 hours,  330hrs ago, by A.Suminas (LT-66-717). And I ve never rotated crankshaft with this bolt. 

My friend, who also has 912is, checked how this bolt is tighten on his engine today. He told it was loosened. And could move it with one hand fingers!