Ok, there is an issue, so fixed versions:
V18.104.22.168.1 for M3.5: https://moodle.org/plugins/pluginversion.php?id=19349
V22.214.171.124.1 for M3.6.1: https://moodle.org/plugins/pluginversion.php?id=19350
If you have previously installed either V126.96.36.199 on M3.5 or V188.8.131.52 on M3.6.1 then with existing (prior to upgrade) grid courses that had an incorrect number of sections will fix themselves 'if' their course settings were not changed. If they were changed and the number of sections or orphaned activities / resources is not what you want then edit the 'course_format_options' table in the database (backup first) and remove any 'numsections' entries for affected course ids, the courses will then 'self repair'.