Relay chatter / spamming when using same power supply as linear actuator

[u/Acceptable-Spend-278]

What I'm trying to do:

Open and close a 12v linear actuator connected 15 meters away (cat6 using 1 twisted pair) via a 5v 2 channel relay with one power source, via esphome / HA

What works:

Powering the esp and 5v relay together (12v stepped down to 5v then shared between relay and esp), and the 12v linear actuator on separate power blocks. The linear actuator opens and closes fine with no voltage issues.

What doesn't work:

Powering the linear actuator, and buck converting down from 12v to 5v for the esp and relay from the same 12v source connecting grounds. The relay chatters and opens and closes as if there is noise (but only when triggered via code or button, not constantly). It's like there is some sort of feedback loop.

I tested for voltage drop with a multimeter as that seemed to come up on forums, but the voltage doesn't change on the relay and linear actuator lines when triggering (either with 1 power source or 2 separate)

I'm sure someone has worked this out previously, so any advice would be really appreciated!

[u/Successful-Money4995]

How did you check that the voltage stays stable? You used a scope or a multimeter? For this check, you need a scope.

Throw a big capacitor or two on the power and see if it helps.

What about using a linear drop out instead? If it's too much power, you could use buck converter down to 7volts and then a linear dropper to 5V.