Node-Red Crashing while node-red-contrib-speedtest is installed

After installing node-red-contrib-speedtest node-red is crashing the whole Time:

● node-red.service - Node-Red
Loaded: loaded (/etc/systemd/system/node-red.service; disabled; vendor preset: enabled)
Active: failed (Result: exit-code) since Sat 2018-07-28 22:46:52 BST; 6s ago
Process: 3918 ExecStart=/usr/local/bin/node-red -u /mnt/dietpi_userdata/node-red (code
=exited, status=1/FAILURE)
Main PID: 3918 (code=exited, status=1/FAILURE)

Jul 28 22:46:51 DietPi node-red[3918]: file using your chosen key the next time you deploy a cha
nge.
Jul 28 22:46:51 DietPi node-red[3918]: ---------------------------------------------------------

Jul 28 22:46:51 DietPi node-red[3918]: 28 Jul 22:46:51 - [info] Starting flows
Jul 28 22:46:52 DietPi node-red[3918]: 28 Jul 22:46:52 - [info] Started flows
Jul 28 22:46:52 DietPi node-red[3918]: 28 Jul 22:46:52 - [red] Uncaught Exception:
Jul 28 22:46:52 DietPi node-red[3918]: 28 Jul 22:46:52 - Error: bind EADDRINUSE 0.0.0.0:5353
Jul 28 22:46:52 DietPi node-red[3918]: at _handle.lookup (dgram.js:282:18)
Jul 28 22:46:52 DietPi systemd[1]: node-red.service: Main process exited, code=exited, s
tatus=1/FAILURE
Jul 28 22:46:52 DietPi systemd[1]: node-red.service: Unit entered failed state.
Jul 28 22:46:52 DietPi systemd[1]: node-red.service: Failed with result 'exit-code'.

The node isn’t crashing because it finds that port 5353 is already in use.
But that shouldnt cause the node or node-red to crash. You should notify the author, normally by opening an issue on github ( follow the link from the nodes page on flows.nodered.org)
But you should be able to restart nodered by deleting the node from the command line and then restarting node-red

I assume you mean "is crashing"?

Yes, it looks like the node is not cleaning up after itself so it leaves the port open and so cannot be restarted then it doubles down on that error by not handling the port already in use error.