I've seen this done by others. They add a layer over that bottom corner for extra support. Often used when dry setting a liner. The best way is to vacuum and start filling the pool. Then come back when liner reaches just under stairs then cut them in. That is a wet set. It only really happens when filling with a truck or replacement liner with a bladder system.
I have seen 2 stairs in my time leak from bad factory gasket track. Under the groove strip there is a gasket sealing it to the stairs. The liner is then sandwiched with the opposing groove and screws, then iner cut, and the finish trim installed. The top groove needs to seal completely edge to edge. Looks a little short in your pic. That can do it. The other thing is they used way too little concrete under the stairs in my eyes. I fill up to 3rd step. It's so hard to compact under there. Nothing worst than hollow steps
Thanks for the response
@jimmythegreek and everyone else.
The PB is a huge d-bag and basically told me I don't know what I'm talking about and I shouldn't be talking to others, I should be coming to them with concerns. I told him last time I did it took 3 weeks and countless emails and phone calls to get a call back from the owner. He ended up coming out on Sunday to take a look and we made amends and he promised to have it fixed on Monday and scheduled backfill for Thursday. Well as you may have guessed they no-showed Monday and Tuesday and ignored my calls and emails until I sent an email mid-day on Wednesday stating the course of action I would be taking if they continued to ignore my communications and refusing to finish the pool (consumer complaint->hiring another company to finish ->recouping damages in court -> truthful reviews everywhere). I got a response within 10 minutes telling me someone will be there within the hour.
The installer (who couldn't be nicer) came out yesterday explained the reasons for the reinforcements in the corners and basically said the same thing that Jimmy did. The only thing that doesn't make sense is that they could have done a wet install since they came late at night and had me fill the pool to the shallow end over night and came back the next day to cut the returns, skimmers, and light. Anyway, he took the cover piece off the gasket and there was a screw missing. However that hole was right next to another screw which makes me think they messed up putting the gasket on initially. Anyway he put another screw in and tightened the rest and we started filling and it looked like that fixed the problem. However I checked this morning and the back of the stairs are wet again in that same spot.
I’m guessing there is a hairline crack in the stairs, but even if that were the case water would still have to be getting past the gasket, right?
The installer gave me his cell and told me to text him this morning if it's leaking, which I did but I'm not sure he's going to come as I had it out with the owner last night after he told me he had to push backfill until next week. We are already beyond the end date specified in the contract (45 working days from dig to patio poured). He gave me some ******** about rain days not counting despite installing half my pool in the rain. Given the owner's response to my concerns and his nonchalant attitude I don't really see a way forward with this PB and I really don't trust him to do anything else. Last night when I thought the leak was fixed, I was fine with that and figured I would just backfill myself and maybe even do it the right way with clean stone. But now that I see the leak isn't fixed, I'm guessing I need to call another pool company to come out and assess the situation.
I can't imagine any reputable PBs looking for extra work right now, nevermind something with so many red flags and potential liabilities. Anyone have any advice on how I should move forward?