I’ve made this recipe about 10 times over the years and it has been full-proof, always coming out perfect. It is also very easy and tastes amazing. See recipe attached.

However I made it for the first time in my current place yesterday and the caramel didn’t set, even though the top browned. I assumed it was a random case of bad luck and made it again this morning (yikes I wasted 4 cans of condensed milk). While it was better, it still didn’t caramelise/set properly. I didn't want to keep cooking it for longer as it was brown on top, and it was obvious something wasn't right. The top had soaked down into the base, meaning the base was soggy as well (rather than firm).

Besides the oven, the only difference from earlier (successful) attempts was using Pams Golden Syrup instead of Chelsea. Every other recipe I have baked in my Bosch oven has worked fine. I used standard bake (as per normal), and baked it near the bottom of my oven.

Any ideas?

I suspect its the condensed milk. You have probably used a different brand. Or the country of origin for the contents has changed. This has happened to me.

Cheesecake this is really odd, I have looked over the recipe and can't see anything obvious that would trip you up and of course you have already made it many times and it has been fine.
My only thing I could think of is that if the topping is too hot then it could soak into the base. My daughters sometimes have that issue with tan square as they re too impatient to let it cool first. However the recipe doesn't tell you to cool the topping first...

Hmm I am perplexed.

I think it is probably the condensed milk.
I have learnt that the 'lite' doesn't work
Some brands have different ingredients, so that could be the reason.
How disappointing

I think I remember getting slightly different results from the golden syrup in a bottle compared to the golden syrup in a tin. From memory also the Pam's bottle syrup was higher in salt than the Chelsea equivalent but that wouldn't make any difference here.

Funny you mention this Helen. Normally I put the cold topping straight on the hot base. However when I made it the first time in the weekend I had about a 15 minute gap due to a visitor. I wondered if this was why it had failed (ie the hot base starts the caramelisation process). So when I made it the second time I put the topping on immediately - and while slightly better it still didn't work.

Re comments on the condensed milk, I used Nestle both times, and not the "lite" version. They were from two different batches of condensed milk, so I can't even blame a rogue batch.

Any thoughts on whether I could try cooking it higher in the oven, at a higher temperature, or fan bake (instead of normal bake)?

Thanks everyone for your ideas :-)

How old is your oven? It might be worth getting it serviced and ask the electrician to test the thermometer- it could be faulty.