Oria theme Search does not work

Hello, since update to WordPress version 5.0.1 (meanwhile I have 5.0.2, but that did not solve the problem) the search function does not work properly. I am using Oria Theme, version 1.09 frome June 2018. If I use the search function looking for example for “Geister” I get only three results, relatet to a new entry. But I have several articles with the word “geister” in the headline and this articles are still in the system. But I cannot search for them. I have tested this with some more keywords with the same result: recently published articles can be found, older articles not. What could be the reason? Does the new WorpPress version cause that problem? When will there be a new version of Oria theme available? And might that solve these problems? Thank you very much for attention and support. Eva

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