How to effectively avoid current drops while stepping down the voltage?
Your question lacks complete details to be answerable and also says 5V then 6V later.

Here is a 25A 6V DCDC with low Ron Push-Pull FETs , low DCR Coil and low ESR Caps.

You may compare your design with this and report differences with results.  This was a free design by TI WebBench based on high efficiency >98%.