I have the Same problem. But it isnt just on 11.3. I currently have CFW, but before i had that still happend to me. My 3ds reboots fine after the error.
Did you read everything? Becouse the thread says: "This might not work on 11.2, so don't be surprised if HANS gives you an error!". But you can use OnionFS just install ahl9.
I may try the new ram site, and download more RAM to my Switch. Not sure if ddr3 is the right ram
for it tho. Edit- no it uses floppy Ram, just like @AncientBoi