Most caching plugins offer the function to combine CSS and JavaScript files to achieve a reduction of the files and thus reduce the loading speed. Especially when combining JavaScript files (depending on the amount of JavaScript files used), there are often errors in the display.
Solution: A good way is to add all used JavaScript files to the exception and in the second step to take them out of the exception one by one in order to determine which file or files might cause the errors. To get a simple summary of all JavaScript files, a list can be exported using the free crawler program Xenu’s Link Sleuth.