Unable to bind socket errors if ESP32 not powercycled between uploads, strange error messages

I think I got this issue on an ESP32 with 2v01 when trying to use MQTT / tinyMQTT. reset(1), reset button, power cycling does not solve the problem. The board can connect to wifi, ping works.
What really puzzles me is that I have an ESP32 with tinyMQTT that works.

With MQTT the error message is ERROR: Connect failed (err 104)
With tinyMQTT the error message is:

ERROR: Connect failed (err 104)
Uncaught InternalError: Unable to create socket

at this call: a.cl=require("net").connect({host:a.svr,port:a.prt},b)

Edit: A simple http get does work.
Edit2: A simple http server works:

function onPageRequest(req, res) {
  print('page req', req);
  res.writeHead(200);
  res.end("Ok.");
}
require("http").createServer(onPageRequest).listen(80);