Column Compression - ERROR 1265 (01000): Data truncated for column

Hello,

Testing MariaDB 10.5, and first time implementing column compression as part of upgrade.

Converting normal columns to COMPRESSED columns seem to work ok.

However, when I want to do an ALTER TABLE later, it appears that I have problems with the compressed columns, even if I'm not changing them.

Example:

MariaDB [mydb]> ALTER TABLE `mytable`
CHANGE `question` `question` VARCHAR(500) COMPRESSED CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NULL DEFAULT NULL,
CHANGE `col2` `col2` VARCHAR(50) COMPRESSED CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL;

Query OK, 3708285 rows affected (1 min 8.067 sec)
Records: 3708285 Duplicates: 0 Warnings: 0

MariaDB [mydb]> ALTER TABLE `mytable`
CHANGE `col2` `col2` VARCHAR(50) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL;

ERROR 1265 (01000): Data truncated for column 'question' at row 8362

MariaDB [mydb]> ALTER TABLE `mytable`
CHANGE `question` `question` VARCHAR(500) COMPRESSED CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci NULL DEFAULT NULL,
CHANGE `col2` `col2` VARCHAR(50) CHARACTER SET utf8 COLLATE utf8_general_ci NOT NULL;

ERROR 1265 (01000): Data truncated for column 'question' at row 8362

–

Any ideas why?