Heating issue

Hi,

So last night we got a 3 yr old APH with a TVT vivarium from someone, and it's heating is just extremely confusing.

We own a large number of reptiles and inverts, but when it comes to this Hedgehog and it's CHE, I'm going bonkers.

So the vivarium is structurally laid out just like this: https://thumb1.zeppy.io/d/l400/pict/303388932281/tvt-two-storey-vivarium-plus-wheel-heat-setup-ideal-for-african-pygmy-hedgehog

The CHE (which I thought was really odd) is mounted to the back wall, pointed towards the doors just like in the picture, and the thermostat that they had on it was an on/off, from experience I understand that although it can be done, it's not really best as that means the CHE is either off or full blast.

Now this is the interesting part - because of the large number of reptile tanks already around her, we can't really have her anywhere except under the window, and even there the lowest that space ever realistically reaches is around 73F, perfect fine for the frogs and stuff around there. Anywhere else in the room exceeds 80F ambient.

So we kept the thermostat in and plugged it in just for over night as we got her quite late in the evening, and would sort it all out today. The thermostat was set at 76/77F (Komodo on/off so not digitally accurate), which in comparison to everything else in the area is damn cold so no thoughts/worries of any heat/fire hazard issues from us.

I check a few hours later though for peace of mind to see how things are going, and the slightest draught must have passed the probe and caused this CHE to go all hands on deck, as I noticed a big patch of obvious heat damage on the floor right above it (you can also see this in the vivarium from google in the picture), grabbing my temp gun it says !208F! so immediately I'm clattering about trying to wrap my head around why this thing has gone haywire. The thermo probe came wedged onto the staircase on the left, so a good 1ft away from the CHE which is not a good idea at all.

So I moved the probe to be right in the middle at the front of the upper floor, held in place by the closed doors, immediately the CHE clicked back off as it was measuring around 80F on the top floor at this point. I thought great I can sleep now.

Daytime today no issues, the CHE doesn't click on at all due to the other heat sources in the room. Night comes and I'm cleaning her poops out etc, had the doors open about a minute (so the probe dropped down back to bottom floor) and put my hand above the CHE again just to check how things are doing - it's back at it again, 1F too low from what the stat is set to and this CHE goes mental.

Does anyone have any idea what I can do here? Realistically, the tank will never drop low enough to harm the Hedgehog without a heat source, but just for my peace of mind and for the Hedgy's health on an oddly cold night, I'd rather keep the CHE in there as a backup.

I've never used a pulse stat before, only dimmers and mat stats, so would a pulse sort this problem? Would it regulate heat enough it wouldn't risk setting the ceiling of the viv on fire?

Could I change placement of the CHE? I thought about this but not sure if the current heat situation would end up setting all the felt/fleece etc blankets and stuff on fire.

Where should I be placing the probe? I've never had a vivarium like with two separate floors, thermostat placement from any experience I have is for things that like to base themselves on a basking spot.

Could I use a heat mat fixed to the underside of the upper floor instead, with the probe attached directly to the mat? I fear this heat wouldn't really go any further than warming the first 1cm of wood it's attached to.

Sorry for the long post, I've just tried to give as much info as possible.

Really appreciate anyone's help on this.