Certificate Code not unique

[vmk-dev]

Describe the bug
so long our moodle created more than 6500 certificates. now we found out that the code IS NOT UNIQUE. we found codes that are used up to 4 times.

Moodle Version(s)
Moodle 3.9.13

To Reproduce
?

Expected behavior
the certificate code must be unique

Screenshots

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Smartphone (please complete the following information):
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Additional context
Add any other context about the problem here.

[wojogun]

for additional questions pls contact me!

[bozoh]

i think i use UUID it's should be unique