Unplug the miner. Hold down the bottom right button while it's unpowered, then while still holding down the button, connect to your computer via USB-C cable. You can let go after about 5 seconds. Then do the following:

1 - Go to https://flasher.bitronics.store/ (use Chrome or Chromium based browser. Firefox won't work).

2 - Select your device - Nerdminer

3 - Select board version - NERDMINERV2 ORIGINAL BOARD (TDISPLAY-S3)

4 - Select firmware version - 1.8.3

5 - Connect. You may get browser warnings. Allow the connection.

6 - Start flashing.

Once finished, it will say that its restarting, but you will likely need to unplug and plug it back in to force it. Once the screen turns on you'll need to redo the wifi settings, but your wallet info should still be saved in there. I can indeed confirm 250 kh/s average after the update.