Deselection when clicking with Highlight Full Row

I use Windows 10 x64. This problem did not happen in Opus 10. I use TeraCopy as my copy program.
I select multiple files and then right click to bring up the menu. When I do my files are deselected. This does not happen every time that I copy files so I have to be aware when it happens so as to copy all the files that I need to. I used Opus 10 since 2012? and never had this happen. It happens when I right-click and before I choose anything on the menu.
Thanks for your help!
Bob Brandt

So as soon as you right-click, the files are deselected?

When it happens, if you open the View menu, are you set to Details mode or Power mode (or another mode, e.g. Thumbnails)?

Does a context menu still appear, or is deselection all that happens? (Is it the context menu for the files, or the one you get when clicking the folder background?)

Is the spacing of the file display such that there are gaps between the selected files which you can click through?

Thanks for your reply. I have solved my own problem. In settings, Preferences, I had the file display mode, details, Always highlight full row checked. I thought that that chose the whole row, but I had to click on the file name to choose it. I have since learned that I have to, after choosing multiple files, right-click on one of the file names to make it copy and not anywhere on the row.
I have now unchecked the Highlight full row and have chosen File selection / highlighting style to Full row and my problem is solved!
Thanks again.