Drives people crazy but you really don't have to bump it back up until it completely drops to zero, and it doesn't matter if it then dropped to zero, say, in the morning and you didn't see it until night. It can sit at zero like that with no problem to the cycle, in fact its better if you don't bump it up too quickly.
Yes, I still feel that from the time of the nitrite spike onward, it doesn't hurt to do the occasional 90% gravel-clean-water-change with ammonia (& baking soda if needed) recharge to get your nitrite and nitrate levels down and to keep your calcium and KH refreshed for the later parts of cycling. Its great practice for beginners to do the gravel clean process and refine the details of what will be an important habit before they have to worry about fish getting in the way.
~~waterdrop~~