Sometimes normal links to pages are not generated by using the typolink viewhelper like this:
<f:link.typolink parameter="{link}">{linktext}</f:link.typolink>
Without changing anything in TYPO3, but just clearing the cache, solves the problem and links are generated again without problem.
Interesting part is, that on a page only the links to one page are not generated, but other works. Example: on page 3 all links to page 4 are not generated, but to page five are working perfectly well.
This phenomenon is not reproducible, it just occurs every now and then. I can't see any errors in the TYPO3 log.
Any suggestions, how to debug?
By analysing the error more in detail I found out, that it occurred because the page was requested and cached with the language parameter L attached. The value of the parameter was a language ID, which is not present in the system.
I updated the configuration in this way, that I just allow the language parameter L with the value 0:
config.linkVars = L(0)
For the moment, this looks promising!