A config or data file is empty or corrupt
What causes it
Gson could not parse a file the game or a mod tried to load. "End of input at line 1 column 1" is an empty file, which is what a crash or kill mid-write leaves behind; "Expected BEGIN_OBJECT but was STRING" is text where JSON was expected. Whatever depended on that file is running on defaults or not at all.
How to fix it
Find the file (the lines just above each error usually name it), back it up, then delete it so the mod regenerates it, or restore it from a backup. If the same file keeps breaking, the disk filled up or the server is being killed while it saves.
Not sure this is your problem? Paste your log and Roastd will tell you which of these it actually matched, and what else it found.
Check your own log