What version of Espruino are you using? There was a bug in setInterval fixed in v68.
See also https://github.com/espruino/Espruino/issues/416 (I suspect it effects intervals as well)
@DrAzzy started
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
What version of Espruino are you using? There was a bug in setInterval fixed in v68.
See also
https://github.com/espruino/Espruino/issues/416
(I suspect it effects intervals as well)