I've been experimenting with a counter top but remembered you cannot merge them without the texture breaking, has anyone ever figured out why this happens or better yet, how to prevent it on a creator level?

It's related to the sims3pack to package conversion, specifically. Counters installed from sims3pack files should be functional.

It's also one of those old semi-myths where the waters are muddied by it often being related to Store content that has been 'decrap'ified. The texture resources between the modular parts probably have some kind of synchronicity or load priority and the decrap tool renumbering at random is sure to obliterate that. CC may suffer from it in a similar way, simply from a connection being overlooked by the creator or because TSRW also renumbers somewhat destructively.

Cloning an EA counter with S3OC (with renumber ticked) and seeing if it has the same issue would be a good start.

Thanks for the informative post and the great tip!