I am aware the planets do appear a bit unstable and shaky far away from the sun. The reason for this is likely due to internal fixed point error in the polar offset maths. For short distances they seem stable enough.
In my map, players can create stars with an ability. Each star spawns six planets around itself. (Buff at the star with persistent effect with offset to determine where the planers are created.) The stars explode in supernovas after a few minutes.
I see that you use a fixed star in the middle of the map as a part of your trigger.
Would it be possible to modify your trigger to make the planets spawned by a star ONLY circle around that star, no matter how many stars there are in the game?
Being able to create stars is a late-game thing in my map. Most games, there will be no stars in the game. When there are, players will have only a few at the same time. After a few minutes, a star will blow up in a supernova, destroying the nearby planets. (And thus cancelling the trigger..?)
Is there a risk that if two stars are created close to each other, planets spawned by the first star start orbiting the other star?
I would suggest making each star its own trigger thread. A local array keeps track of the planets that orbit it. Movement is done using a while loop with a wait at the end of its action block. The loop terminates when the star dies, possibly killing all planets in the process. This means each star gets a dedicated trigger thread so it becomes quite scaleable as far as data management goes.