error -300


all of sudden my app started to give errors (300, NETWORK_REQUEST_TIMED_OUT) on the following code:

 function callURL(url) {
  // Log url
  // Make the request
                "Content-Type" => Comm.REQUEST_CONTENT_TYPE_URL_ENCODED
The errors however only occur on the watch (i own a forerunner 630, but i also have users reporting the same error on other devices (like vivoactive music 3) and not in the simluator. 
It also does not appear to be a timeout, since the error comes directly after the request was done.
I use exactly the same function in another app, and there it works fine, also on my watch.
anyone, since i have complaining users and i have no clue how to fix, Please help! Does anyone know how to fix? or other possible causes then network timeout?
Kr Arnold