I had this same issue back in March. Even the IT computer shop couldn't figure it out nor did Corel give me an real knowledge on how to fix this. I'm using coreldraw 2017. If I try to open any new DXF file or an old one it says it's unrecoverable. So I decided to do a multitude of things. I tried opening it on a another computer in Corel 2017 - didn't work. So I had a back up of my external hard drive and tried opening files from there as well, didn't work. In March, when this happened the first time I bought the home and student version thinking it may open in that, nope. I sent a few files to a friend of mine who said one worked and then all of a sudden none would work. Any clue on why this keeps happening? This is getting incredibly stressful to me and I'm on the verge of learning a new program.
Can you share some DXF files that won't work for you?
MR MRS HEATON.zip