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Out of curiosity, where is the oil sensor? Could they have tried to vacuum oil the oil filler neck or from under the filter.
I believe it's at the bottom of the oil pan. I also changed the spark plugs and was reading if they're not torqued correctly this could happen -- yikes!
I kept having a similar quirk with a 991 GT3. It would barely get driven at that point and when it did it would be an easy drive. Apparently if you did that then moisture would build up and it would think the level was high because of it. The way to fix it (which is why I love Porsche) is to drive that MF hard and long. Then when you park and shut off the engine, open the rear lid and and the oil cap. You could hear electronics and resetting. Give it a minute then restart. All done.
...especially after adding the same amount of oil the second time and not being "overfilled" again... it could have been that?