a building has to breathe..by that I mean expand and contract as the temperature and humidity changes , any movement is only minute but they are built to do just that..they would simply fall apart if they didnt...I would suggest the sub floor below the tiles cracking is prob flexing moving slightly more than elsewhere and the tiles are fixed too firmly across that area so cracking.
Ensure a ' super flexible ' adhesive is used next time they are replaced. You could also add a flexible additive to give it extra flex ( make sure it's a powder mix not ready mixed out of a tub ) then you can use the additive to provide that extra bit of flexibility.
I've only ever had problems with grout breakup g out due to subfloor movement and although used a flexible grout , the sub floor movement was still too much so when re grouting used some additive..problem solved..you will probably find that your installer have not used a flexible adhesive because your sub floor is a concrete slab and unlike a timber sub floor , you dont expect it to flex / move in any way, whereas a timber sub floor can move / flex quite a bit..
Hope this