Please help us help you and fill where relevant:
Your LimeSurvey version: [see right hand bottom of your LimeSurvey admin screen]
Own server or LimeSurvey hosting:
Theme: Server problem
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Does anyone also experienced the problem of "500: Interner Serverfehler Call to a member function getNodeAsArray() on null"? This shows only up when I am trying to open specific surveys within my LS installation (All other survey work fine). These specific survey use specific question templates, but they work on a different  LS installation on a different server.
 

I wonder why you don't provide the relevant information (like LimeSurvey versions).

If one survey is causing issues on one LS installation and not another one, you first check the version number of each LS installation. Same version or difference?
I recommend to copy (or export/import) the "buggy" survey to see if that fixes the issues. Check with a different theme/template to see if the issue is caused by the theme.
If that won't help, I would try to delete parts of the survey in the copy. Sometimes it's one question which causes the trouble on a certain LS version.
Sometimes it's a workaround inside the survey.

Thanks a lot. I use in both installations the v5.2.8+220103. I'll try what you suggested.

Maybe try www.limesurvey.org/manual/Debug_mode