Adobe Acrobat Reader DC: freezes/slowly if protected mode not active

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If we deactivate the protected mode in Acrobat Reader DC, some websites are going slowly. If the protected mode is active, the same sites have normal performance.

Unfortunelly we have to deactivate this flag - but the user cannot work with this speed...

Any hint, how can we deactivate protected mode AND working speedly? (Yes, deleting Adobe Reader would be a solution, but it is a last option...)

We are working with MS Windows 10 and actual MS Edge Chromium browsers.