Errors like 'Definition for element could not be located' and 'preview could not load'

For one page I still get errors at the page in cornerstone:
"Preview could not load"
or (after 10 times reload te page) everything appears but clicking on an element causes the message:
"Definition for element could not be located"
I have had problems with this page in the past. It is a page with a lot of elements so I think it is a memory issue. Is there a way to increase the memory with a plugin in stead of adding codes in php-files?

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Scherm­afbeelding 2026-02-05 om 15.29.51