AutoWikiBrowser sometimes unexpectedly inserts blank lines in pages. Whether this happens, and at what locations, depends on the page and on how many characters are added to or removed from it above the added line. Enwiki example: edit [[1984 1000 km of Monza]]; find and replace "complete", which occurs once near the start, to "complete1". (Use either Normal or Advanced settings.) A blank line 262 is inserted. The same happens for any edit which adds precisely one character (even a multi-byte character) to this page near the start. Adding or removing some other numbers of characters consistently inserts one or more blank lines at repeatable locations. For example, removing one character adds one blank line: 328. Most replacements, such as adding two characters to this page, have no unexpected effects. Double-clicking an added line in the diff does not remove it. Clicking Stop shows the "There are manual changes..." confirmation dialog. I use AWB 184.108.40.206 on Wine 5.0 on Ubuntu 16.04.
The Monza page has now changed and no longer shows the problem. I can reproduce it on enwiki [[1984 Monaco Grand Prix]], where it adds a blank line 351 even with default settings and unticking everything (no find and replace, no general fixes etc., no regex). I have .NET 4.5 (dotnet45) installed (and just updated Winetricks from 20190912 to 20200412).