PHP Warning: Undefined array key “excerptLength”

It seems as though something in your project is triggering the generation of block excerpts with incomplete information. This could be caused by plugins you’re using or even your theme.

For example, are you using an excerpt block in your archives, and was it possibly provided by a plugin?

If you’re unsure, you can identify the cause by deactivating plugins one by one. Once you’ve found the plugin causing the issue, you should no longer see any entries in the error log.