Apex will have the correct answer. Do call them Monday. Sideways trigger slop is not normal. When you call Apex they may ask you questions about trigger and trigger block dimensions or appearance, so if you haven't fixed it yourself it's probably going to be best to have things disassembled. You may need some precise measurements and/or close up photos for them to help you.
However, my guess would be that you might have slightly spread the trigger axis ears on that small center trigger mounting block. There isn't much room for them to spread, but it is even more unlikely that Apex sent out a trigger that was too narrow.
A fix would be to remove the whole trigger assembly and fit the top of the trigger between those ears while out of the gun. No slop. You'll probably have to tighten the ears closer to the trigger.
Then add the slide stop and insert the slave pin to hold all three pieces and the trigger return spring together, properly aligned. Insert in the frame. Add the locking block.
Mounting the frame in a cushioned vise helps free up both hands.
Carefully work the trigger axis pin through everything. If you need to use a hammer, things are not aligned and you may spread the far side axis ear by hitting it with the end of the pin. You may need to wiggle components slightly while pushing on the pin. It does take some pressure, but it is more finesse than force.
I believe that will fix your problem, but I am not a gunsmith nor an Apex employee. It just makes sense to me having done a half dozen of these installs.
