As mentioned many times above (very good advice) it seems like you have a voltage drop problem for whatever reason. Please pursue this with the appropriate pros as detailed above very well.
If you are curious to "see" what's happening for yourself you can purchase this at Amazon for ~$28. It will read out true RMS voltage continuously.
https://www.amazon.com/Poniie-PN2000-Electricity-Electrical-Consumption/dp/B0777H8MS8/ref=sr_1_3?cri...
I find mine very useful in the watt readout with individual pieces plugged into it. Simply to see start start-up wattage versus idle wattage.
Plug this into the wall and plug the treadmill into it.
This suggestion in no way negates your need to find a true cause.
Regards,
barts
If you are curious to "see" what's happening for yourself you can purchase this at Amazon for ~$28. It will read out true RMS voltage continuously.
https://www.amazon.com/Poniie-PN2000-Electricity-Electrical-Consumption/dp/B0777H8MS8/ref=sr_1_3?cri...
I find mine very useful in the watt readout with individual pieces plugged into it. Simply to see start start-up wattage versus idle wattage.
Plug this into the wall and plug the treadmill into it.
This suggestion in no way negates your need to find a true cause.
Regards,
barts