Cracked wall - recurring

[u/Coffee2698]

Hi all,

Last year, I repaired this crack with filler and painted over it. Everything looked fine initially, but a few weeks later, the crack reappeared.

Now, around 7 - 8 months later, I've decided to open it up and investigate further (see photos). To my surprise, the crack appears to be approximately 6 cm deep. It looks like it's located where two bricks meet, just below a window.

There are quite a few cracks around the house that have reappeared after being filled, but this one seems a bit more serious and concerning than the others.

I know it doesn't look great at the moment, but I was wondering whether I could fill the deeper part with some repair mortar (the type that comes in a tube, similar to silicone/caulk), then finish it off with filler and scrim tape to help prevent it from cracking again.

I was also considering using Toupret Fill-Flex Flexible Filler instead of mortar, but the instructions mention a maximum filling depth of 1 cm, so I'm not sure it would be suitable.

Has anyone dealt with something similar? What products or repair methods would you recommend, and is there anything I should avoid?

For context, the house is only 6 years old and came with a 10 year structural warranty. Given that several cracks have reappeared throughout the house, do you think this is something worth raising with the builder or warranty provider? Or am I overthinking it, and is it likely just a cosmetic issue - not sure how a 6cm crack is cosmetic but I have to think about it.

I'd really appreciate any advice or suggestions before I attempt to repair it again.

Thanks in advance!