My friends had the same problem in a country house. The tiles were laid a few years ago, the base is brick, they don’t remember what kind of glue, and the seams haven’t been grouted yet!!! As a result, the tiles fell off in places along with the brick, and the entire brick peeled off. There won't be an original photo, but this photo shows very clearly what happened, although the steps are a little smaller. Now they, my friends, want to restore the steps. Please tell me how to do it right? What needs to be done with the base before laying the slab so that the base becomes more or less stable??! 
In your example, the brick base is placed directly on the ground. It is also clear that porous brick has significant water absorption. Thanks to this, moisture from the soil can easily penetrate into the brick base, and under the influence of seasonal factors (especially temperature fluctuations), changes occur that we clearly observe on the surface. You shouldn’t be surprised or upset, because in this case such a process is inevitable. Below I will give two solutions to the questions asked.
Solution 1 is drastic. Disassemble the brick base completely, pour the foundation or pillars of concrete, make waterproofing, install the base of the stairs, tiling, install a canopy over the porch. This approach will preserve the porch covering for decades.
Solution 2 is simple. Carry out restoration of the existing porch using materials from the entry-level price segment. Then, as necessary, approximately once every 2-3 years, restore the coating and base.
Yes, there is still a long way to go before the distance gap is filled. I agree with the previous post: either renew the porch every season, or completely dismantle it, and then follow the instructions. You can also buy a couple of ready-made flights of concrete stairs and install them directly on the old brick base. Fill the sides with 20 centimeters of concrete. Then cover everything with tiles or leave it as is. I pulled off such a trick 8-9 years ago. The staircase is still in excellent condition.
By the way, in the forum “ Steps with correct cladding ” in the second comment on the diagram it is clearly readable that the base is concrete or reinforced concrete. If you dismantle the porch and rebuild it, write here what you will use to seal the space gap - cardboard, foam, air, etc.