Steps to reproduce:

1. For an example, you can take either of the two templates SMART by Zabbix agent 2 where there is an LLD rule to discover the prototype metric SMART {#NAME}: Get disk attributes: SMART {#NAME}: Percentage used -> smart.disk.percentage_used{#NAME}. The above metric prototype is never created.
2. Next, you need to rename the word Percentage -> percentage and save this change.
3. After the next discovery, we make sure that the LLD rule has started working and a prototype metric like SMART {#NAME}: percentage used started to be successfully created.
4. Next, we rename the LLD metric prototype name in this way: SMART {#NAME}: used percentage . After that, at the next discovery we again make sure that the LLD metric prototype is successfully created and functions normally.
5. Next, we rename the LLD metric prototype name in this way: SMART {#NAME}: used Percentage . After that, at the next discovery we make sure that the LLD metric prototype is no longer created and therefore does not function.