TYPO3 RTE: Saving mathematical/greek symbols doesn

Question

I need to display some mathematical/greek symbols in the RTE and later in the frontend. Inserting them via copy/paste or the "Insert characters" option works great, but as soon as I save the text, the inserted symbol get's replaced with a question mark and T3 throws following error:

1: These fields of record 56 in table "tt_content" have not been saved correctly: bodytext! The values might have changed due to type casting of the database.

I think there is an issue with the character set of T3 or my DB, but I don't know where to start looking.

Answer 1

Tested on my 7.6.8 and it seems to work OK. When I login to my mysql and run this query:

SELECT default_character_set_name FROM information_schema.SCHEMATA
    WHERE schema_name = "7_6_local_typo3_org";

(7_6_local_typo3_org is database name) it returns:

+----------------------------+
| default_character_set_name |
+----------------------------+
| utf8                       |
+----------------------------+
1 row in set (0.00 sec)

and also collation:

SELECT default_collation_name FROM information_schema.SCHEMATA
    WHERE schema_name = "7_6_local_typo3_org";
+------------------------+
| default_collation_name |
+------------------------+
| utf8_general_ci        |
+------------------------+
1 row in set (0.00 sec)

Then also I have in my my.cnf (mysql config file):

character-set-server = utf8
collation-server = utf8_general_ci

Answer 2

Similar problem when pasting HTML with UTF-Icons into Raw-HTML content-element in TYPO3-8.7.x but it works when i encode the symbols, for example:

<span class="menuicon">&#8986;</span>