I found an edge case in scanner that results in an assert() failing. The document is:
abc: def: 'xxx ' ghi: 'yyy'
And the issue is caused by that line-wrapped 'xxx'. The next entry needs to be aligned with the first otherwise it's just a normal parsing failure. Result:
 Parsing 'crashtest': lt-run-parser: scanner.c:1113: yaml_parser_save_simple_key: Assertion `parser->simple_key_allowed || !required' failed.
0.1.5 and 0.1.6 are affected.
(found with AFL fuzzing)