Those "skipping" lines are perfectly normal.
Searching for some string is much faster than displaying each and every line on screen. Therefore if you search for a word, less will scan the file for that word and once it finds a line it will display only that page of lines where it found the word.
If you scroll back using your terminal you will see those "skipping" lines.
If you want to go backwards in your text just use the proper keys like arrow keys. This will move you through the text as it is without any "skipping"s.