I have now found the "bug" in the test album. There is a significant difference in the search results. I'll try to explain it, even though I do not know if it's always the case.
The "bug" is noticeable when using prev / next. For me, I see it more clearly, as I show current number / total number.
If an album and images are listed in the search results, the images whose album is also listed are displayed in their original static album. The images whose album is not listed in the search result are displayed in a stand-alone dynamic album. (I call this search result dynamic album).
If now both are mixed, then the search result dynamic album is left, if prev / next reaches an image, whose album is listed in the search result.
You can do it the same way in the test album. Here are a test with three different search results.
Make a new search each time (not within).
http://demo.zenphoto.org/page/search/
Theme basic light.
1.)
search for "nebel".
Total matches for nebel: 2
(0 albums, 2 images)
The albums of the two images are not listed. If you click on an image, you get into a search result dynamic album with only 2 images (prev/next). All is fine.
2.)
search for "a".
Total matches for a: 8
(2 albums, 8 images)
For every image their album is listed. Click the images. All images are displayed in their original static album. Not realy fine, if 1st is considered.
3.)
search for "nebel | album1".
Total matches for nebel OR album1: 3
(1 albums, 2 images)
It is getting interesting now. In one of the images also their album is listed, in the other, the album is not listed.
To reproduce the "bug" it is important to click on the image /album2/Cosmos05.jpg.html
A dynamic album is displayed (with only 2 images. (prev / not next).) If you click on "prev" the search result dynamic album will be left because the album of this image is listed in the search result. You notice that when you click "next" again. Now a different image is displayed and "next", ie more than 2 images.
If you click the image /album1/Cosmos01.jpg.html first, the original static album of this images will be displayed. In this case, immediately leaves the search result dynamic album, or does not even get into it.
My wish would be that all images are always displayed in a search result dynamic album and never leave this. The leave should be possible only on the breadcrumbs. But still albums should be listed in search results.