Strange behavior or RAND in MariaDB: Single RAND delivers more than 1 result

When running the following query:

SELECT productid 
FROM product 
WHERE productid=ROUND(RAND()*(SELECT MAX(productid) FROM product));

The result should be 0 or 1 results (0 due to data gaps, 1 if a record is found), however it results in multiple results a good number of times (very easy to reproduce, 90% of queries have more than 1 result).

Sample output:

+-----------+ | productid | +-----------+ | 11701 | | 20602 | | 22029 | | 24994 | +-----------+

(Number of records in DB is about 30k).

Running a single SELECT RAND() always results in a single result.

Who can explain this behavior?