Which host software, OS, and Corona version?
What is changing in the scene? This part looks like it hasn't changed, but the scene could have become more complex (somewhere outside of this crop) and 10 passes is no longer enough. Often, noise limit is a better choice for animations for that reason, as 10 passes may be fine while the room is empty, but not enough as furniture animates into view (just to invent a possible animation :) ). Also by default Corona is adaptive, that is, it decides where to put processing power depending on light sources, objects etc. so could be that something in the image outside of the crop is needing more processing power and 10 passes is not enough now for this area to clean up (again, noise limit as a target works better for that reason). Does this happen if you render frame 227 on its own directly (single frame, just 227), or only when frame 227 is reached once running from the start?