Glad it worked. I have had occasional similar problems with DesignCAD files and occasionally with Word files. However, I use DesignCAD far more than any other program so you would expect that to be the place I saw more problems.
For what it is worth, I had the greatest number of problems with V17.2. I had several files that did very strange things. After moving on to V18, V19 and V20 I have seen very few problems that were not actually the result of some mistake that I made. A huge number of bugs and shortcomings have been corrected since V17.
One thing you should watch out for with V17 is an overflow in the group count. It has a limit of only about 16,000 group IDs over the entire life of the file. Every time you create a new group a new Group ID is created and the Maximum Group ID counter is incremented. If you use the file as a starting place for a new drawing (for title block, borders, etc.) the Max ID counter is carried over to the new drawing. Deleting all the groups in the old drawing will not change this.
Deleting existing groups does not roll back the Max ID counter. It keeps increasing steadily as you work on a drawing. Since you have been working on your drawings for years it is possible that this counter will overflow, even though you may currently have a relatively small number of groups in the file. After this happened to me in a V17 file the program would crash any time I tried to edit the file. I could open the file and look at it (rotate the view, zoom, etc.), but if I tried to edit the file it was CTRL-ALT-DEL time.
Solutions to this problem have been posted on the Forum, but they are not perfect. The problem has been fixed in later versions by increasing the Maximum ID number to a truly huge value and adding a function that repacks existing group IDs and resets the Max ID counter.
Based upon my experience you would be wise to upgrade to V20. However, you may see a few problems with dimensions. Occasionally text will be positioned differently than it was in V17, and arrows on arc dimensions sometimes do odd things. You may have to edit these to get them back like they were, and dimensions do not work exactly the same in newer versions. But for the most part you should have fewer problems in V20.