Could you please supply the data you're attempting to post? You say it's erroring out on an asterix (*) however the last error that you posted is showing \x92 which is an apostrophe.
There isn't any filtering that happens server side for some users that don't for others, unless you're allowing HTML postring.
Additionally, could you open the offending table and take a screenshot of the table structure so we can validate that the cells are indeed utf8mb4_general_ci
Do you have SQL logging enabled?
