On an EPOCH game, the Alien Traders seem to move right up to the sector before my main base is at. They camp out there and as soon as I drop figs they destroy them, as soon as I drop mines, they run into them. Can't twarp a planet there to blast them, one of the Alien Traders has 100K figs. If I attack one of them, they all attack me, and there is like 20 of them and growing. Yet they hardly ever go into my base sector, on the rare occasion that they do, they get blasted by my quasar cannons.

Is this normal for a game? Shouldn't they just move on because they cannot get into my base sector, which is in a dead-end?

I'm using this game as a training game, to improve on my Red Playing.

Any tips or hints on how to get rid of the aliens? I destroyed some of them, but more showed up.

Sounds like you might have one of a couple things happening, you could have your base right next to their spawning area and that could be why there are so many there. The other is they could be going through a one way and getting trapped in that sector, I have noticed aliens are kind of strange when they go through one ways, they have a tendancy to want to go back the way they came and they cant so they end up milling around where they came through the one way at. It makes a good trap for aliens and if you can get anyone to come into that sector they are dead meat.

Not a one-way, as they lawnmower my sector figs in the tunnel that leads to the dead-end. It is a 5 sector deep tunnel and they clear out all sector figs until just before the dead-end and then hang out there.

I have a word for it, "Seagulling" because like Seagulls that notice you have a box of popcorn, they tend to stick around and won't go away. Even if you feed them some Popcorn, they will stick around for more or attack you for it.

Is it possible that one of them found my planet and the rest are trying to take it over, but due to some bug in TWGS, they can't?

OK, anything is possible. But we are talking probablility. As Shorty said, you may be near the "Spawning" area. This is where the aliens reggenerate into the game.

It is not likely they are after your planet unless you have it in "Alien Space". As you said, they just "Seagull" in your area.
When the game is setup, the sysop can adjust how agressive the aliens are. From punching bags to killling machines. [xx(]

They are more like punching bags, never attack me unless I attack one of them, then all 20 hit me at the same time. It is very funny when that happens.