I was having the exact same issue until I unplugged the camera. Although I was also having issues with the SD card with read/write speeds of ~2MB/s. Even after unplugging the camera I could not process a .3mf file, the system would completely freeze up and hang during the “unpacking .3mf…” phase and would never complete. Also couldn’t send prints over WiFi…
I replaced the SD card with a high quality Sandisk card, sent a few files initially over WiFi and it worked great! Until I decided to plug in the camera again. I can once again no longer send prints over WiFi and unpacking .3mf files seems to be getting slower with every print. Tried reformatting the card, deleting old files etc etc to no avail. Needless to say, they need a firmware update.