Slit in waste pipe - how?

[Newchapter25]

I recently had a leak from my upstairs loo located next to the bath aa the pipe came off completely and caused water damage through the kitchen ceiling. I had a plumber out to fix it a few weeks ago and no issues since. Until now. When draining the bath, it leaked through the ceiling causing quite a bit of damage again. The loo also happens to be blocked with no visible blockage. My questions are, what would cause a new pipe to split like this? Could it have simply been damaged by accident upon installation? would a new loo blockage cause the water to backup and leak when flushing / draining the bath hence why I’m only having a noticeable issue now? And lastly, what are the odds of this being done by someone on purpose, I can’t help thinking it looks sliced but I hope
I’m wrong? (I do have my reasons
for that last question). I will be getting a plumber out again but it’s going to be a couple of days due to the holidays unfortunately. Thank you.

I follow the leak detective on TikTok and some of the damage he comes across on pipes and things can just be accidental and done on (crappy) installation, others are where it’s been snagged on something or a screw has gone through. Often they haven’t actually caused a leak for several months, or sometimes years.
A loo blockage can cause flooding. We had this recently in an office. Someone had left it blocked. It had an out of order sign on so hadn’t been used for several hours waiting for maintenance to sort, it suddenly started leaking into the main sink area without anyone even flushing it, they assumed just water pressure on the seal.
Toilet should be on separate waste to bath due to how it’s processed. Sewerage is different to grey water.

Ultimately you’d find it difficult to prove it was done on purpose and someone trying to get more work would hide it better and do a small screw hole or something. Any sharp bits of wood on any of those joists/supports?
Did you have an argument with the plumber, is that why you are thinking on purpose?

Thank you for your reply. No arguments with the plumber, he’s a nice chap and doesn’t seem to be in it for the money. My suspicion lies with someone that has access to the house and motivation to cause me a headache. Lots of things have broken over the past couple of months and I’m sure it is pure coincidence but the crazy lady paranoia wheels are twitching.

I have had a better look with a torch now and can see that there is another more suspect looking issue further down the pipe. I’ll attach a photo.

Ahh I see.
It does look like you have further issues. I hope the tears in the pipe are all just coincidental. It’s bad enough dealing with stuff like this, without worrying someone is purposely doing it.