EXCEL: Nested IF-Function only returns #value

i have a switch statement which decides which if function to execute. But although it seems pretty right to me it returns #value! in parts where the switch matches.

=SWITCH(XLOOKUP(E2;$M$2:$M$15;$N$2:$N$15);"Case1";IF(OR(SEARCH($O$2:$O$99;C2)); "OK"; "Check Cluster");"Case2";IF(OR(SEARCH($P$2:$P$99;C2)); "OK"; "Check Cluster");"Case3";IF(OR(SEARCH($Q$2:$Q$99;C2)); "OK"; "Check Cluster");"Case4";IF(OR(SEARCH($R$2:$R$99;C2)); "OK"; "Check Cluster");"Case5";IF(OR(SEARCH($S$2:$S$99;C2)); "OK"; "Check Cluster");"Kein CLuster")

I already tried the following steps:

• Checked for typos (in Europe ; is the right separator)
• Checked referenced cells for value errors
• The XLOOKUP-Function works

So it has to do with the IF-Function. Anyone of you guys got an idea?