Yesterday, I told a lot of disappointed folks that follower counts are often inaccurate.
A few chimed in that home instance follower counts are always accurate. This is not true either.
Scenarios for why home instance follower counts could be inaccurate is if instance:
1. Turns off follower count data
2. Gets re-installed
3. Migrates to another server or different software
4. Deliberately misrepresents follower counts
Bottom line: do NOT use follower counts as any core KPI metric!