If you notice, that forum -a-gasket on that cover did not cause this. That was installed correctly. The forum a-gasket was used correctly. maybe a little heavy but that was not bad for the way it was used.
Most use this stuff right out of the tube. Squeeze it out on what you need it on, then slap it together. You just did it wrong.
The forum-a-gasket needs to skin over. depending on temp and all it could take 20 mins for this to skin over, to cold and it won't skin over. You can tell in the photo that indeed this did skin over. Look at how the forum-a-gasket formed little balloons when the cover use installed. That is how it should look if to much is used.
I had an A&P when I fist purchased this airplane get this stuff in the engine. He did as I said and just slapped it all together. I could tell you the horror stories of what he did but why.
Now why do I put so much forum-a-gasket on that cover. I do not trust that wire to hold that cover in place. You remove that wire and you have to work to get that cover off. Use very little and it will just fall off. It happened to me after that A&P worked on my airplane. Then he went nuts with the stuff and did not know the correct way to use it, I had the stuff everywhere.