It is certainly not a bad design but it probably should not cost much. Everything in this construction went wrong. Probably as a result of poor adhesive material, incorrect detailing, inadequate inspection, and poor implementation by not following the Instructions for Use.
The contractor has undoubtedly saved a few coins, but now you have a damage that far exceeds this saving. Not to meantion the displeasure and inconvenience for the owner/resident.
Finally the cheapest is always the dearest in the end… Recognizable? To avoid these damages, follow the opinion of experts from TWEHA.