Provide a demonstration, such as a minimal program that exhibits the problem.
If I knew how to reproduce the problem, I wouldn't be asking for places to look for the problem!
In changing from one server setup to another, transferring the data from one instance of MariaDB to another via SQL dumpfiles, and running the same Perl scripts albeit under a different version of Perl, we have gone from correctly rendering webpages to webpages containing numerous  characters.
An example blog post on our test site. The  characters did not appear prior to the change.