Does Each Mechanical Chime Need a Power Kit?

I have a large house that has two mechanical chimes. I installed the Ring Pro about 6 months ago and mostly working fine, but lately have noticed the indoor chimes sometimes not ringing when the doorbell is pressed. (Sometimes they do, sometimes they don't.) The "Device Health" says Transformer voltage is good everytime I check it and is typically over 4000 mV. Question: I only recently thought of this, but do I need a Power Kit installed on BOTH indoor mechanical chimes? Right now I only have it on one.