I discovered that when users tried to insert an message with Emoji’s (specific example from iOS phones) the comment could not be places.
So with the help of these topics:
– https://projectdmc.org/support/topic/problem-when-saving-with-emoji/
– https://github.com/WordPress/gutenberg/issues/19552
– https://projectdmc.org/support/topic/problem-displaying-an-emoji/
I came up with 2 database queries that solved the problem:
ALTER TABLE wp_gwolle_gb_entries CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
ALTER TABLE wp_gwolle_gb_log CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
This solved the problem for us!
Hopefully others can use this solution for future use.