Ok, this may not sound like much help, but I can promise it will work. Take it to your local shop and have it setup (should be cheap). While it is being setup read through the setup guides on this site and elsewhere, and learn how to do it yourself to save you cash in the future.
If you would like an explanation to your problem, its your action is most probably too low, which in itself is an easy fix, but you would benefit from a setup to get you on your way.
Tuning to A is not something that can be done with standard gauge strings and a normal action (either the action must be raised, or the string gauge raised). If you play in drop tuning a lot it may be worth getting some higher gauge strings, then having your bass setup.
Theres a little too much here to cover in one post, but keep reading and you will soon get the hang of it.
Hope this helps.
PS; it has nothing to do with your tuning keys

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