Some cached website images does not load or slows down website loading for 15 seconds

Hello,
Some specific cached website images/js does not load or slows down website loading for 15 seconds.
Problem is resolved only in case of enabling Development Mode in Cloudflare panel, or creating custom URL rules with Cache bypass enabled.
When Development mode is turned off and caching is not disabled for these custom images/js files, problem repeats.
What to do to resolve this problem?
Thank you for the help.

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