The Letter of Guarantee has a weird format:
letter_of_guarantee_xxxxxxxxxx_.json: ASCII text, with very long lines, with CRLF, LF line terminators
That makes it look weird in both xed and vi:
Can you try to rename it to .txt? It's basically a text file with multiple sections, public key, signature format (?), signature and an actual json only at the end.
Maybe it helps; I've opened with notepad++ under Windows and looked pretty good/understandable (not that I've checked anything else than recovering the session, which can be done with the link too).