I live in Canberra where it's really cold during winter & really hot in the summer. Whilst I do use post-mix kegs for storage, I do have numbers of bottles stored out in the garage.
I have always thought that the bottles (usually some amongst those stored but not the vast majority) with condensation was caused by a non-airtight seal.
Apparently, I was way off course.
This web site explains why there is condensation in our spirit bottles (a sign that the seal is airtight ...):
https://vinepair.com/articles/ask-adam-why-is-there-condensation-in-my-spirits-bottle/