Tiny beads/flecks of uncooked dough all through my bread

I'm not sure exactly what aspect of my bread-making is at fault here, but this is close to my tenth loaf, and each one has turned out a bit differently as I've tried to work on my technique to produce better results. A couple of times the loaves have been perfect but the last three have consistently had these little doughy flecks all through the loaf, surrounded by a nice well-cooked texture.

Here is a picture of today's loaf:

I live in Brisbane, Australia, and most days during this learning curve have been at the very least in the high 20's, and often around the 30-31C mark (85-90F). The humidity can get quite high too, often 60-90%.

I'm using a crusty white bread mix from Laucke Mills, which is basically bread flour with some kind of bread improver mixed in. Here are the steps I take:

1. I activate the yeast by adding it to the specified quantity of water (tepid, roughly lukewarm) along with a teaspoon or so of sugar, mix it up and let the yeast activate (5-10 mins)
2. I add the specified quantity of flour to the mixing bowl and add the activated yeast and water mix a well in the middle, then mix with a large metal mixing spoon until a have a sticky hunk of unkneaded dough. It generally looks like the pictures in other guides I have read.
3. I flour the breadboard with a thin-ish layer of flour (I have a really large breadboard, so there's enough space), spread the flour around with my hands and then tip the rough, sticky doughy ball into the middle.
4. I start kneading, and have been trying to speed up the rate at which i fold, knead and turn, because, despite using the exact quantities of flour and water specified, I find the stickiness of the dough makes it stick to my hands really quickly, and if that happens, I end up having to rub my hands to uncake the dough onto the side (I'm not letting the caked bits get back into the dough, so that can't be the issue). Even then, it's hard to knead the dough to a point where I get that thin gluten window every guide out there claims that I should be able to see after 10-15 minutes of kneading.
5. Eventually the dough ball seems consistent enough, so I then proof it in a lightly oiled mixing bowl for 40 minutes or so, as that's how long it takes in this weather to roughly double in size.
6. Next I punch the dough down a bit and then upend it back onto the now-clean breadboard, flatten it out a bit to try and release the gas, then shape it into a roughly bread-like shape.
7. I allow it to rise in the tin (with baking paper) for roughly 30 minutes, as that's how long it seems to take to get a significant rise, then I put it in the oven, which supposedly should be around 220C by now. I also put a tray of boiling water at the bottom of the oven, as various guides seem to recommend.

After about 40 minutes, the result is what you see in the picture. On this occasion I tried to put it back and each time I pulled it out, I cut off a test slice to see if the extra time had been the issue. The doughy bits did cook a bit more by the third replacement, but eventually the crust got too brown and hard and I knew it was time for a postmortem.

Would greatly appreciate any advice.