[mrmikel]

Left and right double quotation marks, often use “ and ”, so you can do a search and replace in the html and replace them with less fine but universally readable ". You can use a program like Notepad++.

As I recall this is a problem with LRF files than EPUBs.

You can also get odd characters by the code pages not matching. There is a place in the conversion settings where you can experiment trying different ones.

You might do what I have done from time to time. Search for &# in the html and when you find something you don't recognize, copy it to the clipboard and paste it into a Google search window, It will mostly not find anything, but it will display what it is.

Then you can decide what you want to do with it and all the other &# codes.