I think the problem is related also to:
RAK3172 Arduino IDE RUI3 uploading problems (2nd time) - RUI - RAKwireless Forum
Need help to Upload firmware in RAK3127 using Arduino ide, and also not respond AT command - WisBlock - RAKwireless Forum
If you can, run AT+BOOT through Serial just after the startup of the module so you should be able to upload a new firmware.