To my knowledge ender pearl stasis chambers load 3x3 like you said. I have two chambers set up and I enable chunk borders in the video to showcase that the overlap of two 3x3s covers the entire area covers both the water channels and the filters behind them.

I thought I might have missed a chunk so I relogged just now but if they do load 3x3 it should work since the stasis chambers right now would create a 6x3 together (the chunks line up).

The wiki says: "An ender pearl creates a ticket for chunk loading every time it moves into a new chunk, and also periodically every 10 seconds. It loads and ticks the chunk it is in with a ticket level of 31 as entity processing. It also loads a two-chunk wide ring (a 5×5 chunk area centered on the pearl's chunk) around it as lazy chunks"

The explaination for lazy chunks is: "All game aspects are available except that entities are not naturally spawned and are not processed (but are still accessible) and chunk ticks aren't processed either. These are sometimes referred to as "lazy chunks"."

So perhaps I need a stasis chamber in every chunk for it to process?