@Myst and Snk
I made a full guide on digging, i tested three major areas and the crab spawn rate wasnt a problem.
A few weeks later and we were able to do this.
I'm pretty sure something happened to digging. Also crabs hardly drop any shells, we got like 4 shells total out of all of those crabs.
The spawn rate of crabs per shovel used to be like three crabs. Now its close to 6 or 7.