Michael Howell

I noticed that, too. At first I thought that I left the gate open and a zombie got loose, but it was closed and the mob spawned in a lit hallway next to where my spawn grinder is. If this isn't resolved, it's going to make things super difficult. On the upside, double piston extenders seem to work without issues in bedrock... So, maybe that's the trade off?

I noticed this same issue when I was playing yesterday.  I am on XB1 Bedrock Beta, Experimental Mode, Survival.  The spawner always stopped when I put a single torch on it so I could tweak my space to make a more efficient grinder, in the past.  Yesterday, I figured I'd try to convert the space from a zombie spawner to a drowned one.  Placed a torch on the cage and immediately got a zombie (I assumed I timed it just right with the spawn tick).  Then I had two more show up.  So, I placed torches all around and underneath the cage, as well as four more along the walls of the space (well past the necessary light level needed to stop spawning).  I spent the next few hours getting beaten up by zombies while attempting to change out my grinder build.  Nearly lost my sword and all my gear before I walked away and did some other stuff.  What worries me is that this might be a bug that will affect another spawner that I have a torch on from WAY before now.  Hopefully, this will be resolved for normal difficulty (at least), because it's super frustrating at times.