Moving a TikiWiki Site from one domain to another
Ulrich,
I originally misread your Tiki versions — are you suggesting you moved from a newer version to an older one? (I originally misread it as you were moving from 24 to 26 (bootstrap), but your post says 26.4 to 26.2) — maybe this is creating problems with rendering, although it should not.
Another thing that someone suggested to me is a different PHP version on the new server, which may cause things to break (which I have encountered).