Crumbling brick/plasterboard behind leaking shower

[LauraOwen]

Hi
Recently our bathroom shower has been leaking water into the hallway below (just a tiny bit of water randomly not everytime we shower).
This happened over a year ago and we had a guy redo the sealant and it stopped.

Today I finally got round to redoing the sealant. But as I started to remove the old sealant I have found a large crack/hole between the tiles and the shower base, it looks like there is a big chasm where the plaster/brick(?) has crumbled. I have attached photos of the crack and one of under the shower (but this is not what you can see from above).

I would really like some advise please.
Is this:
a) a big issue and do we need to sort this out? And basically take apart the shower and take of the tiles to investigate further?

b) Or is this not really a problem and can I just reseal it?

 

[blup]

You would expect it to be like that as plaster or even brick would have been removed when installing the tray. So long as it is properly sealed again and there is no damp or rot in the joists it shouldn’t be a problem

 

[Madrab]

Primary issue (edit spell) with that is usually the legs - the tray is on a riser kit and that has probably compounded the issue, allowing the tray to move and eventually burst the seal. That then allowed to tray to move more and more and on it goes. Looks like once the tray has moved then the gap that appeared had been filled with silicone to tray and seal it up, but that would never be a permanent repair.

As it sits that gap is really too large/wide to even attempt to bridge it with silicone, it will never work long term. Does the tray moves? Can it be pushed back in against the wall?

If you are looking to do it right though then ideally the tray needs to be removed and re-set into the space - ideally using a wooden plinth instead of those legs. Without seeing what's in front of the tray it's hard to see what might be need to remove the tray.