@warran – forget enclosures until it gets cold down in your dungeon! When it gets cold, resin goes a bit thicker and failures are more likely; but atm you’re not probably going to see much difference. I run my Anycubic 4k mono in an unheated workshop overnight and it’s only really from Nov. onwards I worry about trying to heat the printer.

Reasons for failure?
Temperature is a big one. But I honestly don’t think that’s your issue right now.

You tend to get failures in specific parts of the bed if the FEP is too tight/too floppy (if the FEP is too floppy, you’ll get failures in the middle and more success around the outsides of the build plate – if it’s too tight, the opposite).
Thinking about what happens when your resin printer plate lifts: the resin is stuck between the FEP and the print bed. The FEP has a degree of “give” to it. Lifting the head pulls the cured resin and needs to rise enough that the printed resin eventually releases off the FEP (and stays stuck to the previous layer).
If the FEP is too floppy, the printed resin never releases off the FEP.
If it’s too tight, with no give at all, the printed resin is equally as likely to stay stuck to the FEP as it is the bed (and you only need it to stay stuck to the FEP once for it to stay there for the rest of the print!)

Lift speed. Lower it.
I usually lift between layers at about 35-40mm/sec. A lot of printers can go much faster than this. But then it’s like ripping off a plaster. Again, thinking about how the printer works, you want to lift (relatively) slowly, so as you pull the FEP up with the printed layer, there’s enough time for the FEP to give, then release, then spring back into place. If your lift speed it too fast, you’re “ripping the plaster off”.

Add delays between layers.
This used to be important for my Anycubic Photon (less so for my 4k mono, but I still include it). When the head has lifted, turn off the UV array (the purple lights) and give it a few seconds (I use any value up to about 4 seconds). Why? Well, firstly it’s the ripped plaster thing again. But ALSO it allows the UV matrix time to cool down (so it’s not switched on almost all of the time).
Without delays, your UV light is on for 2.5-10 seconds (depending on 3d printer type), then it goes off and the head lifts. If you lift the head really quickly and return, then whack the UV light on again, it’s on for more time than it’s off. This can cause the printing bed to warm up over time. A warm LCD, exposed to UV, breaks down quicker than a cold one.
(my original Anycubic Photon had an expected LCD lifetime of about 400 hours; I was still running the original LCD after more than twice this, because I allowed cooling time between layers).

Don’t just delete islands!
Thing about an upsidedown traffic cone – the problem with just deleting islands, is you’ll remove almost all of your traffic code, until it reaches a point where it touches another object. Now you’ll be printing not a tiny little point that gradually gets bigger over multiple layers, but a massive, flat, square area, possibly connected to another shape by just a few pixels.
There’s more to checking your files than just deleting islands! Sometimes you need to connect islands to other objects, or add in some “filler pixels” over a number of layers to make good, strong bonds.

So first thing, check your supported STLs for unsupported shapes and support them.
Then check the sliced file for islands and *fix them*.
Then make sure the temperature isn’t too cold for printing (by which we’re talking below 15C or so – at this time of year, given it’s unseasonably warm in much of the UK, this is unlikely to be an issue; if you feel like you’d want to put the heating on to be comfortable yourself, that’s when print failures might occur due to temperature if you don’t).
Then check your lift speed isn’t too high (40mm/sec ish should be fine – it slows down your print, but if you’re leaving it to run overnight, does it matter if it takes 4hrs instead of 3.5hrs?)
Add a time off delay between layers (I use 4 sec but this is probably overkill).

Lastly, make sure you’ve got your exposure time (per layer) set correctly.
Too high and your minis will appear “soapy” (overexposure).
Too low and you’re also get failures!

The great thing is, once you’ve got your printer set up right for your conditions, it can be as repeatable and reliable as any of your other tools!