Voltage drop on octoprint

my pi 3b was working great running octoprint. now i input 5.15v but pi is only giving me 4.75 to 4.9
has any one got a fix .
many thinks

Not enough details to suggest a fix.

When your RPi 3B was working great, how was it powered (as much detail as possible)?

What change did you make (and why)? Where is the 5.15v measured? Where is the 4.75 to 4.9v measured? What gage wire are you using?