Yup, not enough villagers and your lower spawn floor is 1 block too high. And what's with the villagers running loose behind the doors?
The spawn floors and drop hole are also too large. Only 16x16 blocks are valid spawn locations, and golems are 1.4 blocks wide so a 2x2 drop is all you need. The larger 19x19 spawn floors offer no benefit, since the horizontal spawn area is only 16x16, and the large 3x3 center drop actually reduces the valid spawn space by cutting 9 blocks out of the spawn floor instead of just 4. You have additional corner blocks to make the water flow further that cut out a few additional valid spawn blocks. I use dual 18x18 floors with a 2x2 drop which hits more than 98% of golem spawn attempts, and makes water placement easy.
Oh, and the whole thing is too close to the nearby village, so they likely merged and shifted the golem spawn area outside the trap. Minimum distance between mock villages to prevent merging is 65 blocks, and that will allow you to stack up to 4 villages vertically (more villages = more iron).
So ... pretty much everything is wrong with your iron farm. Sorry.
Personally I use 3x3 drop chutes in my Iron Farms as it is (or was) possible to get the scenario below. The chances of two golems spawning in such a manner that they reach the chute together is rare (and only possible if you have 20+ villagers) but it is a thing as my screenshot shows and i had it happen a few times on my farm. Basically one golem stops the other from dropping and they get stuck there.
My floors are also 19x19, but i have the corners filled in 2x2, and I just have 15 water source blocks each side, which is the simplest water arrangement for me. Might not be optimum spawning area, but the loss is minimal.
Personally I use 3x3 drop chutes in my Iron Farms as it is (or was) possible to get the scenario below. The chances of two golems spawning in such a manner that they reach the chute together is rare (and only possible if you have 20+ villagers).
Simple solution to that is not to have 20+ villagers.
There is no advantage to more villagers in legacy farms, and as you have shown, there may be a disadvantage. Most of my farms have 40 doors per village, which spawns 14 villagers. I think I had 48 in one of my early designs (for aesthetics), but that's still only 16 villagers.
With dual 19x19 spawn floors using 3x3 drops and 2x2 corner blocks, in the best case scenario you miss 2.1% of spawn attempts. In a worst case scenario you miss 2.23%. With 18x18 floors and 2x2 drops you only miss 1.87%.
Yes, that's a small difference, but why use more resources to get less iron, even if it's only a little less?