In SX Microcontrollers, SX/B Compiler and SX-Key Tool, George Herzog wrote:

The capacitor is intended to be very close to the IC to filter out noise and spikes created by other ICs sharing power.  But the actual value of the capacitor can vary from 1mf to 0.01mf as required.

The lower the value, the faster the spikes that it catches.  

On the other hand, you may have a problem if there are two ground paths between the devices.  Noise might loop around or reflect.  How many ground pathways do you actually have?  More is not better.

That high bit might be a reflection.  You could change the value to the capcitor [like 0.22mf or 0.47mf] and see if it still stays away.  After a board is built, usually engineers will test it before going into production.  If one of these capacitors needs changing, they just tweak the value to get optimal reliablity.  No big thing.

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