So I got my hotbin in mid-July. It took about two weeks before it was reading internal temperatures of 60C. All through August it maintained its vigour, greedily reducing everything I threw into it. Me and my hotbin were best buds!

But those were the halcyon days. Since the beginning of September I haven't had it above 40C. For the last few weeks its internal temperature has scarcely hit 30. I'm absolutely mystified as to why.

I'll list the things I'm told the hotbin needs and describe how I'm addressing them.

External temperature
Sure, it was hotter outside in summer. But the temperature outside scarcely dropped in September. And the hotbin is insulated and is supposed to operate even in winter. So I don't think it's that.

Bulking agent
I've used a lot of bulking agent. I've used the whole bag that came with the bin. Since then, I've been using wood chippings I blagged off a tree surgeon in the park. I took half a wheelie bin full of wood chippings off the tree surgeon, and I've nearly got through that. So, since mid-July, I must have put the best part of half a wheelie bin's worth of wood chippings into my hotbin. I'm pretty sure I've been providing enough bulking agent.

Composting material
I have an allotment and a family. Out hotbin mainly gets fed food waste (about two full caddies a week) and leafy material (weeds, cut grass, nettles etc) from the allotment. This is all supposed to be stuff the hotbin loves. Frankly, it should be going apeshit. So I don't think it's being fed the wrong things.

Frequency of feeding
Generally twice a week, with the material described above.

Correct moisture level
I'm aware that he material I'm giving it (see above) is on the moist side. Fortunately, I own a shredder and we get no shortage of junk mail and I have years of old bank statements. So I use plenty of shredded paper - I think 50% by volume compared to the food waste / plant waste etc I'm putting in the bin. I'm also ripping corrugated cardboard into little bits and chucking that in. So if there's a problem with the compost being too moist, it's certainly not because I'm not providing the recommended amount of shredded paper.
The paper is the office-grade stuff, and judging by the one load of compost I've removed from the bottom of the bin so far, it's all broken down nicely. That compost, to my surprise, was not especially wet (not slimy or anything), but I'm new to composting so I'm not sure what level of moistness to expect in the finished product.
Having said all that, it does appear that the bin is producing an awful lot of leachate. The concrete floor the bin sits on is stained brown with the stuff.

Airflow
(Obviously also related to moisture level above.) This is where I suspect the problem may be. If the bacteria don't get enough oxygen, they can't process the stuff quickly, right? I removed perhaps 9 inches of mostly-composted material from the bottom of the bin a week ago, hoping that would improve airflow and get the temperature up, but it hasn't made any difference whatsoever. I've just recorded the internal temperature of the bin and the thermometer grudgingly hit 30C.
Does the compost in the bin not block airflow as the bin fills up? If so, what can I do about it?
I'm also wondering if some component of the bin itself is blocked. Is there a part of it - the grill at the bottom for example - which can get blocked up and block the airflow? Should I be somehow accessing components of the bin and checking / unblocking them?
Is there a way I can check directly whether airflow in the bin is impeded?

The reason I paid £180 for the hotbin was because I wanted to be able to compost the ghastly perennial weeds my allotment grows with gay abandon. The temperature is now too low for me to be able to do that, so my hotbin is now effectively a white elephant taking up space in my garden. I'm really not happy about it.

Has anyone else been in this situation and been able to reverse it? Can anyone suggest a remedy based on the information I've provided above?

Thanks in advance,

David