I just found this as I helped the company I work for moved from MySQL 5.6 to MariaDB 10.1.14 more than a year ago. Currently Amazon is encouraging us to go to Aurora but when I ran Aurora/MariaDB tests MariaDB won most of them. The reason I’m posting this at all is that one of the MariaDB ‘things’ dealing with settings was that when I tried to tune any of the parameters it would bounce back to ‘defaults’ if I did not use precise values for caches, memory setting and what not. They had to be exact, or that would not accept the values. This might have been one of the issues with you inability to run your queries. Our very complex BI queries worked brilliantly on MariaDB.