The specific test periods is a yellow flag. Failure to advance should be a thing, and it shouldn't be because someone isn't showing up enough. If they are not technically prepared for the next rank, then they shouldn't get a stripe or a belt. Period. Advancing early should also be a thing for those whom grasp things quickly as well. The techniques probably aren't flawed, but if the sparring is compliant, and little effort is required to advance: That is definitely a problem. 90 days could be the earliest time for advancement, and that might be okay. If there are more than a few belts it isn't necessarily wrong. Compare yourself to your peers and those higher rank than you. Has everyone been improving?
Is your school part of a larger organization? Start looking for schools of the same style or organization where you plan to move, and see if they may honor your current belt rank. Some may also offer you a test to see where you're at too. It also doesn't hurt to find training partners from different styles as well depending on your skill level.