Cracks in the tile joints in the shower

After 7 years in the new house, we have now noticed that fine hairline cracks have formed in the grout between the tiles on the back side of the shower. (so not in the silicone) This affects 3-4 grout lines stacked on top of each other below the fittings. Behind the tiles is drywall, which surrounds the vertical shaft to the ground floor.

The tiler from back then currently has fully booked schedules and is a bit "slow" to come by and take a look. Whether he will see anything without removing the tiles is another question.

In principle, everything under the tiles should be sealed. This was also thoroughly checked by our building surveyor at the time.

Now there are 2 options
1.)
If the sealing were not damaged, the hairline cracks would basically not be a problem. If I have the grout exposed and regrouted, I see the risk that the sealing might be damaged.

2.)
If, on the other hand, the sealing is damaged (e.g. by the shower fitting above) or something is leaking, the drywall could swell/work and that could cause the hairline cracks.

I am currently a bit torn regarding the further course of action.
What is a sensible approach (especially given that there might possibly be an insurance claim)?
Should I have our building surveyor (who is also a construction expert) from back then take a look, or just have a tiler repair it, or involve the insurance, which might send its own expert?

So the insurance will probably not get involved at first, because there is no damage yet. At least none that you know of so far, since the damaged joints are not an insurance claim right now. I would most likely try to have this or another good tiler come by for an inspection and a repair quote. Alternatively, the expert, who probably won't be able to tell you much more anyway and will want to get paid to say that it should be repaired.

So find a tiler, have them assess it, and then have it repaired based on the quote.

Thank you very much for your opinion.

In another forum, I came across a post that shows exactly the same cracks. The pictures posted there could also be from us.
The general tone there was, no problem as long as you don’t hold the water jet directly on it. The joints would never be properly sealed anyway. The sealing is provided by the waterproofing behind it. That doesn’t sound illogical either, provided the waterproofing isn’t cracked somehow as well.

However, I’m probably a bit influenced by something right now.
Our neighbors currently have a major insurance claim in the bathroom and surrounding rooms because water has been gradually leaking from the sewage pipe there for years. Now everything up to the floor slab is wet.
They had to move out for 3 months, and after drying, the bathroom will be completely redone from the screed up.
Lucky in misfortune, the insurance pays.

@ Musketier: cschiko is completely right and you yourself have already seen with the neighbor what can happen. So: have it repaired thoroughly as quickly as possible. Old saying: Water (even drop by drop) always finds its way. Good luck!

What is true, however, is that joints are never completely sealed! Sealing always occurs underneath, yet of course professionally executed joints are "tighter" than partially crumbled joints. Because water remains (more) in there and then finds its way!

What I see as a bit of a risk is that when the joints are cut out with a multicutter, plunge saw, or similar tool, the underlying sealing and the drywall board are exactly damaged. That would be fatal in my opinion.

How gypsum can swell gradually, I have experienced myself in the house because the plaster rails of the exterior plaster were attached with gypsum-containing material during rework. Our house construction company had to replaster our entire house within the warranty period due to the partly 1-2cm thick cracks in the plaster. The subcontractor who botched the work was already insolvent at that time because they performed poor work everywhere. This then broke the neck of our general contractor in the second step.