Did you mean .vmf file?
HammUEr has no support for compiled bsp files.
oops, I meant to say .vmf
Can you put the vmf on pastebin or google drive or something so I can test it locally?
Sorry for the delayed response. Here is the vmf that imports just fine in 4.18, but it won't in 4.15.
I don't have access to my code archive at the moment, so I can't really check with an actual 4.15 build, but my guess is it's got something to do with the displacements?
(Also, this is a decompile, and decompiles are technically not supported. Maybe try opening it in HammUEr and saving it back to clean up whatever the decompiler did?)