fatal error, conflict with another plugin

Dear Support team,

Would yo be so kind to help with a critical error we get with the latest versions of Ultimate Member?(since version 2.1.21)
The conflict appears with plugin “mb YTPlayer PLUS for background videos” Version 3.5.7 | Door Pupunzi (Matteo Bicocchi.)
When this plugin is deactivated, ultimate member runs fine.

I have the report with error messages available for you.

Our WP version is 5.8.2 with PHP 7.4.9.

Thanks in advance
D.V.

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