Removing tiles on shower floor area that has been tanked.

Unfortunately yes it will and until you start its hard to say how far it will go. But to be on the safe side it is a good practice to start over and make it right.

You're probably gonna have to take out the tiles on the floor and the bottom course of tiles on the wall, as taking the floor tiles up will definitely damage the tanking. The reason for taking off the bottom course of wall tiles is so you can re-tank that area up to 100 mm from the floor. I'm not going to lie, it will be a difficult job to make perfect, but there seems to be a problem with a laying of the tiles as the grout should not come loose which would suggest either movement in the tile or the subfloor, also grouting may not be fully reaching the depth of the tile. You could try to take out most of the grout with a grout-rake or multi tool then reapply grout mixing with PVA depending on type of tile, but if there's movement in the tile this is really a temporary solution. Hope this helps, but I recommend using a professional as not being able to view the actual job, there can be other underlying problems.